Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $192.52   4.428%   $201.0448   $201.04   $201.05   $201.00  
  Purchase #2 $47.88   13.274%   $54.2356   $54.24   $54.25   $54.20  
  Purchase #3 $141.35   12.561%   $159.105   $159.11   $159.10   $159.10  
  Purchase #4 $160.95   10.457%   $177.7805   $177.78   $177.80   $177.80  
  Purchase #5 $123.58   13.477%   $140.2349   $140.23   $140.25   $140.20  
  Purchase #6 $209.52   4.660%   $219.2836   $219.28   $219.30   $219.30  
  Purchase #7 $53.89   12.564%   $60.6607   $60.66   $60.65   $60.70  
  7 purchase totals = $929.69       $1,012.3451   $1,012.34   $1,012.40   $1,012.30