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 $91.93   3.614%   $95.2524   $95.25   $95.25   $95.30  
  Purchase #2 $29.84   13.726%   $33.9358   $33.94   $33.95   $33.90  
  Purchase #3 $215.52   7.669%   $232.0482   $232.05   $232.05   $232.00  
  Purchase #4 $155.55   3.427%   $160.8807   $160.88   $160.90   $160.90  
  Purchase #5 $186.96   13.224%   $211.6836   $211.68   $211.70   $211.70  
  Purchase #6 $103.25   10.832%   $114.434   $114.43   $114.45   $114.40  
  Purchase #7 $78.74   10.639%   $87.1171   $87.12   $87.10   $87.10  
  7 purchase totals = $861.79       $935.3518   $935.35   $935.40   $935.30