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 $57.27   9.422%   $62.666   $62.67   $62.65   $62.70  
  Purchase #2 $236.29   3.743%   $245.1343   $245.13   $245.15   $245.10  
  Purchase #3 $104.62   13.691%   $118.9435   $118.94   $118.95   $118.90  
  Purchase #4 $26.31   13.644%   $29.8997   $29.90   $29.90   $29.90  
  Purchase #5 $193.56   8.365%   $209.7513   $209.75   $209.75   $209.80  
  Purchase #6 $21.68   13.352%   $24.5747   $24.57   $24.55   $24.60  
  Purchase #7 $109.62   9.105%   $119.6009   $119.60   $119.60   $119.60  
  7 purchase totals = $749.35       $810.5704   $810.56   $810.55   $810.60