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 $90.85   4.517%   $94.9537   $94.95   $94.95   $95.00  
  Purchase #2 $60.83   7.425%   $65.3466   $65.35   $65.35   $65.30  
  Purchase #3 $117.50   7.412%   $126.2091   $126.21   $126.20   $126.20  
  Purchase #4 $150.52   3.315%   $155.5097   $155.51   $155.50   $155.50  
  Purchase #5 $58.63   12.575%   $66.0027   $66.00   $66.00   $66.00  
  Purchase #6 $69.96   10.687%   $77.4366   $77.44   $77.45   $77.40  
  Purchase #7 $220.30   12.370%   $247.5511   $247.55   $247.55   $247.60  
  7 purchase totals = $768.59       $833.0095   $833.01   $833.00   $833.00