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 $22.61   11.694%   $25.254   $25.25   $25.25   $25.30  
  Purchase #2 $247.27   3.335%   $255.5165   $255.52   $255.50   $255.50  
  Purchase #3 $117.83   12.798%   $132.9099   $132.91   $132.90   $132.90  
  Purchase #4 $189.53   11.428%   $211.1895   $211.19   $211.20   $211.20  
  Purchase #5 $46.88   4.461%   $48.9713   $48.97   $48.95   $49.00  
  Purchase #6 $203.55   3.779%   $211.2422   $211.24   $211.25   $211.20  
  Purchase #7 $59.91   11.812%   $66.9866   $66.99   $67.00   $67.00  
  7 purchase totals = $887.58       $952.0700   $952.07   $952.05   $952.10