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 $84.81   9.230%   $92.638   $92.64   $92.65   $92.60  
  Purchase #2 $46.49   4.576%   $48.6174   $48.62   $48.60   $48.60  
  Purchase #3 $13.73   7.831%   $14.8052   $14.81   $14.80   $14.80  
  Purchase #4 $204.81   6.421%   $217.9609   $217.96   $217.95   $218.00  
  Purchase #5 $42.57   11.104%   $47.297   $47.30   $47.30   $47.30  
  Purchase #6 $195.65   7.370%   $210.0694   $210.07   $210.05   $210.10  
  Purchase #7 $228.86   3.114%   $235.9867   $235.99   $236.00   $236.00  
  7 purchase totals = $816.92       $867.3746   $867.39   $867.35   $867.40