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 $108.86   9.414%   $119.1081   $119.11   $119.10   $119.10  
  Purchase #2 $166.95   12.152%   $187.2378   $187.24   $187.25   $187.20  
  Purchase #3 $136.43   11.655%   $152.3309   $152.33   $152.35   $152.30  
  Purchase #4 $53.89   8.584%   $58.5159   $58.52   $58.50   $58.50  
  Purchase #5 $68.85   11.408%   $76.7044   $76.70   $76.70   $76.70  
  Purchase #6 $23.84   13.578%   $27.077   $27.08   $27.10   $27.10  
  Purchase #7 $117.65   7.690%   $126.6973   $126.70   $126.70   $126.70  
  7 purchase totals = $676.47       $747.6714   $747.68   $747.70   $747.60