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 $175.86   11.218%   $195.588   $195.59   $195.60   $195.60  
  Purchase #2 $54.62   8.182%   $59.089   $59.09   $59.10   $59.10  
  Purchase #3 $169.91   6.457%   $180.8811   $180.88   $180.90   $180.90  
  Purchase #4 $125.49   10.460%   $138.6163   $138.62   $138.60   $138.60  
  Purchase #5 $5.72   9.532%   $6.2652   $6.27   $6.25   $6.30  
  Purchase #6 $234.76   6.594%   $250.2401   $250.24   $250.25   $250.20  
  Purchase #7 $166.43   8.748%   $180.9893   $180.99   $181.00   $181.00  
  7 purchase totals = $932.79       $1,011.6690   $1,011.68   $1,011.70   $1,011.70