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 $34.76   3.414%   $35.9467   $35.95   $35.95   $35.90  
  Purchase #2 $158.38   5.500%   $167.0909   $167.09   $167.10   $167.10  
  Purchase #3 $217.82   8.197%   $235.6747   $235.67   $235.65   $235.70  
  Purchase #4 $75.47   5.849%   $79.8842   $79.88   $79.90   $79.90  
  Purchase #5 $219.72   11.551%   $245.0999   $245.10   $245.10   $245.10  
  Purchase #6 $155.87   10.519%   $172.266   $172.27   $172.25   $172.30  
  Purchase #7 $19.49   8.221%   $21.0923   $21.09   $21.10   $21.10  
  7 purchase totals = $881.51       $957.0547   $957.05   $957.05   $957.10