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 $66.53   9.127%   $72.6022   $72.60   $72.60   $72.60  
  Purchase #2 $109.52   7.141%   $117.3408   $117.34   $117.35   $117.30  
  Purchase #3 $51.30   13.481%   $58.2158   $58.22   $58.20   $58.20  
  Purchase #4 $51.76   4.533%   $54.1063   $54.11   $54.10   $54.10  
  Purchase #5 $41.71   5.790%   $44.125   $44.13   $44.15   $44.10  
  Purchase #6 $214.67   5.372%   $226.2021   $226.20   $226.20   $226.20  
  Purchase #7 $38.77   13.786%   $44.1148   $44.11   $44.10   $44.10  
  7 purchase totals = $574.26       $616.7070   $616.71   $616.70   $616.60