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 $83.81   13.730%   $95.3171   $95.32   $95.30   $95.30  
  Purchase #2 $183.98   9.314%   $201.1159   $201.12   $201.10   $201.10  
  Purchase #3 $169.59   7.464%   $182.2482   $182.25   $182.25   $182.20  
  Purchase #4 $173.76   4.790%   $182.0831   $182.08   $182.10   $182.10  
  Purchase #5 $48.86   7.111%   $52.3344   $52.33   $52.35   $52.30  
  Purchase #6 $6.69   11.388%   $7.4519   $7.45   $7.45   $7.50  
  Purchase #7 $153.39   7.508%   $164.9065   $164.91   $164.90   $164.90  
  7 purchase totals = $820.08       $885.4571   $885.46   $885.45   $885.40