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 $182.73   7.109%   $195.7203   $195.72   $195.70   $195.70  
  Purchase #2 $189.53   6.782%   $202.3839   $202.38   $202.40   $202.40  
  Purchase #3 $62.31   9.114%   $67.9889   $67.99   $68.00   $68.00  
  Purchase #4 $216.52   4.127%   $225.4558   $225.46   $225.45   $225.50  
  Purchase #5 $28.68   12.642%   $32.3057   $32.31   $32.30   $32.30  
  Purchase #6 $58.64   11.726%   $65.5161   $65.52   $65.50   $65.50  
  Purchase #7 $154.33   5.725%   $163.1654   $163.17   $163.15   $163.20  
  7 purchase totals = $892.74       $952.5361   $952.55   $952.50   $952.60