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 $95.48   6.583%   $101.7654   $101.77   $101.75   $101.80  
  Purchase #2 $69.98   4.437%   $73.085   $73.09   $73.10   $73.10  
  Purchase #3 $97.39   5.130%   $102.3861   $102.39   $102.40   $102.40  
  Purchase #4 $162.71   7.669%   $175.1882   $175.19   $175.20   $175.20  
  Purchase #5 $210.90   7.319%   $226.3358   $226.34   $226.35   $226.30  
  Purchase #6 $167.31   6.401%   $178.0195   $178.02   $178.00   $178.00  
  Purchase #7 $234.98   11.751%   $262.5925   $262.59   $262.60   $262.60  
  7 purchase totals = $1,038.75       $1,119.3725   $1,119.39   $1,119.40   $1,119.40