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 $61.49   3.672%   $63.7479   $63.75   $63.75   $63.70  
  Purchase #2 $104.54   7.486%   $112.3659   $112.37   $112.35   $112.40  
  Purchase #3 $193.89   5.272%   $204.1119   $204.11   $204.10   $204.10  
  Purchase #4 $74.26   5.186%   $78.1111   $78.11   $78.10   $78.10  
  Purchase #5 $139.37   11.148%   $154.907   $154.91   $154.90   $154.90  
  Purchase #6 $30.83   11.263%   $34.3024   $34.30   $34.30   $34.30  
  Purchase #7 $104.70   7.464%   $112.5148   $112.51   $112.50   $112.50  
  7 purchase totals = $709.08       $760.0610   $760.06   $760.00   $760.00