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 $96.26   5.783%   $101.8267   $101.83   $101.85   $101.80  
  Purchase #2 $115.32   9.175%   $125.9006   $125.90   $125.90   $125.90  
  Purchase #3 $21.71   13.311%   $24.5998   $24.60   $24.60   $24.60  
  Purchase #4 $46.69   3.374%   $48.2653   $48.27   $48.25   $48.30  
  Purchase #5 $237.69   6.129%   $252.258   $252.26   $252.25   $252.30  
  Purchase #6 $235.46   9.152%   $257.0093   $257.01   $257.00   $257.00  
  Purchase #7 $169.44   3.436%   $175.262   $175.26   $175.25   $175.30  
  7 purchase totals = $922.57       $985.1217   $985.13   $985.10   $985.20