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 $146.94   10.530%   $162.4128   $162.41   $162.40   $162.40  
  Purchase #2 $208.37   8.309%   $225.6835   $225.68   $225.70   $225.70  
  Purchase #3 $32.60   4.648%   $34.1152   $34.12   $34.10   $34.10  
  Purchase #4 $53.28   8.260%   $57.6809   $57.68   $57.70   $57.70  
  Purchase #5 $36.94   8.183%   $39.9628   $39.96   $39.95   $40.00  
  Purchase #6 $176.94   4.360%   $184.6546   $184.65   $184.65   $184.70  
  Purchase #7 $212.61   13.646%   $241.6228   $241.62   $241.60   $241.60  
  7 purchase totals = $867.68       $946.1326   $946.12   $946.10   $946.20