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 $141.51   9.194%   $154.5204   $154.52   $154.50   $154.50  
  Purchase #2 $119.38   12.338%   $134.1091   $134.11   $134.10   $134.10  
  Purchase #3 $51.98   12.415%   $58.4333   $58.43   $58.45   $58.40  
  Purchase #4 $118.76   5.784%   $125.6291   $125.63   $125.65   $125.60  
  Purchase #5 $245.95   5.822%   $260.2692   $260.27   $260.25   $260.30  
  Purchase #6 $232.54   5.631%   $245.6343   $245.63   $245.65   $245.60  
  Purchase #7 $61.56   9.735%   $67.5529   $67.55   $67.55   $67.60  
  7 purchase totals = $971.68       $1,046.1483   $1,046.14   $1,046.15   $1,046.10