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 $194.28   5.185%   $204.3534   $204.35   $204.35   $204.40  
  Purchase #2 $44.68   4.170%   $46.5432   $46.54   $46.55   $46.50  
  Purchase #3 $185.95   10.508%   $205.4896   $205.49   $205.50   $205.50  
  Purchase #4 $154.37   6.839%   $164.9274   $164.93   $164.95   $164.90  
  Purchase #5 $73.90   13.693%   $84.0191   $84.02   $84.00   $84.00  
  Purchase #6 $226.84   6.667%   $241.9634   $241.96   $241.95   $242.00  
  Purchase #7 $95.35   4.379%   $99.5254   $99.53   $99.55   $99.50  
  7 purchase totals = $975.37       $1,046.8215   $1,046.82   $1,046.85   $1,046.80