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 $158.93   10.507%   $175.6288   $175.63   $175.65   $175.60  
  Purchase #2 $193.69   4.393%   $202.1988   $202.20   $202.20   $202.20  
  Purchase #3 $138.73   9.601%   $152.0495   $152.05   $152.05   $152.00  
  Purchase #4 $230.98   13.814%   $262.8876   $262.89   $262.90   $262.90  
  Purchase #5 $126.35   8.215%   $136.7297   $136.73   $136.75   $136.70  
  Purchase #6 $154.57   8.829%   $168.217   $168.22   $168.20   $168.20  
  Purchase #7 $19.70   8.582%   $21.3907   $21.39   $21.40   $21.40  
  7 purchase totals = $1,022.95       $1,119.1021   $1,119.11   $1,119.15   $1,119.00