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 $60.78   3.176%   $62.7104   $62.71   $62.70   $62.70  
  Purchase #2 $195.57   3.645%   $202.6985   $202.70   $202.70   $202.70  
  Purchase #3 $56.30   4.368%   $58.7592   $58.76   $58.75   $58.80  
  Purchase #4 $120.85   3.779%   $125.4169   $125.42   $125.40   $125.40  
  Purchase #5 $106.83   10.279%   $117.8111   $117.81   $117.80   $117.80  
  Purchase #6 $85.46   9.241%   $93.3574   $93.36   $93.35   $93.40  
  Purchase #7 $60.56   5.673%   $63.9956   $64.00   $64.00   $64.00  
  7 purchase totals = $686.35       $724.7491   $724.76   $724.70   $724.80