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 $201.69   3.797%   $209.3482   $209.35   $209.35   $209.30  
  Purchase #2 $29.58   11.468%   $32.9722   $32.97   $32.95   $33.00  
  Purchase #3 $212.53   10.322%   $234.4673   $234.47   $234.45   $234.50  
  Purchase #4 $36.89   11.210%   $41.0254   $41.03   $41.05   $41.00  
  Purchase #5 $202.45   11.139%   $225.0009   $225.00   $225.00   $225.00  
  Purchase #6 $152.98   7.452%   $164.3801   $164.38   $164.40   $164.40  
  Purchase #7 $212.99   7.243%   $228.4169   $228.42   $228.40   $228.40  
  7 purchase totals = $1,049.11       $1,135.6110   $1,135.62   $1,135.60   $1,135.60