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 $45.84   4.629%   $47.9619   $47.96   $47.95   $48.00  
  Purchase #2 $217.30   4.284%   $226.6091   $226.61   $226.60   $226.60  
  Purchase #3 $191.91   5.866%   $203.1674   $203.17   $203.15   $203.20  
  Purchase #4 $210.83   8.385%   $228.5081   $228.51   $228.50   $228.50  
  Purchase #5 $76.78   6.793%   $81.9957   $82.00   $82.00   $82.00  
  Purchase #6 $69.37   8.506%   $75.2706   $75.27   $75.25   $75.30  
  Purchase #7 $83.52   11.489%   $93.1156   $93.12   $93.10   $93.10  
  7 purchase totals = $895.55       $956.6284   $956.64   $956.55   $956.70