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 $202.80   13.397%   $229.9691   $229.97   $229.95   $230.00  
  Purchase #2 $237.66   11.614%   $265.2618   $265.26   $265.25   $265.30  
  Purchase #3 $111.61   5.391%   $117.6269   $117.63   $117.65   $117.60  
  Purchase #4 $67.95   6.681%   $72.4897   $72.49   $72.50   $72.50  
  Purchase #5 $48.40   12.638%   $54.5168   $54.52   $54.50   $54.50  
  Purchase #6 $247.47   5.233%   $260.4201   $260.42   $260.40   $260.40  
  Purchase #7 $102.64   7.665%   $110.5074   $110.51   $110.50   $110.50  
  7 purchase totals = $1,018.53       $1,110.7918   $1,110.80   $1,110.75   $1,110.80