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 $98.49   3.254%   $101.6949   $101.69   $101.70   $101.70  
  Purchase #2 $193.71   5.344%   $204.0619   $204.06   $204.05   $204.10  
  Purchase #3 $6.82   9.741%   $7.4843   $7.48   $7.50   $7.50  
  Purchase #4 $131.98   7.295%   $141.6079   $141.61   $141.60   $141.60  
  Purchase #5 $42.93   5.758%   $45.4019   $45.40   $45.40   $45.40  
  Purchase #6 $203.31   6.817%   $217.1696   $217.17   $217.15   $217.20  
  Purchase #7 $24.70   3.262%   $25.5057   $25.51   $25.50   $25.50  
  7 purchase totals = $701.94       $742.9262   $742.92   $742.90   $743.00