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 $82.95   12.791%   $93.5601   $93.56   $93.55   $93.60  
  Purchase #2 $217.75   12.338%   $244.616   $244.62   $244.60   $244.60  
  Purchase #3 $158.46   3.238%   $163.5909   $163.59   $163.60   $163.60  
  Purchase #4 $51.39   9.299%   $56.1688   $56.17   $56.15   $56.20  
  Purchase #5 $75.71   11.843%   $84.6763   $84.68   $84.70   $84.70  
  Purchase #6 $101.55   6.342%   $107.9903   $107.99   $108.00   $108.00  
  Purchase #7 $240.72   7.314%   $258.3263   $258.33   $258.35   $258.30  
  7 purchase totals = $928.53       $1,008.9287   $1,008.94   $1,008.95   $1,009.00