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 $65.26   10.593%   $72.173   $72.17   $72.15   $72.20  
  Purchase #2 $86.84   10.492%   $95.9513   $95.95   $95.95   $96.00  
  Purchase #3 $61.75   5.775%   $65.3161   $65.32   $65.30   $65.30  
  Purchase #4 $227.97   3.394%   $235.7073   $235.71   $235.70   $235.70  
  Purchase #5 $62.97   6.216%   $66.8842   $66.88   $66.90   $66.90  
  Purchase #6 $57.26   3.657%   $59.354   $59.35   $59.35   $59.40  
  Purchase #7 $141.50   7.302%   $151.8323   $151.83   $151.85   $151.80  
  7 purchase totals = $703.55       $747.2182   $747.21   $747.20   $747.30