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 $54.46   12.791%   $61.426   $61.43   $61.45   $61.40  
  Purchase #2 $234.85   5.391%   $247.5108   $247.51   $247.50   $247.50  
  Purchase #3 $7.92   10.654%   $8.7638   $8.76   $8.75   $8.80  
  Purchase #4 $53.49   12.459%   $60.1543   $60.15   $60.15   $60.20  
  Purchase #5 $163.37   10.664%   $180.7918   $180.79   $180.80   $180.80  
  Purchase #6 $96.38   3.267%   $99.5287   $99.53   $99.55   $99.50  
  Purchase #7 $93.90   8.395%   $101.7829   $101.78   $101.80   $101.80  
  7 purchase totals = $704.37       $759.9583   $759.95   $760.00   $760.00