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 $59.95   5.505%   $63.2502   $63.25   $63.25   $63.30  
  Purchase #2 $43.95   5.850%   $46.5211   $46.52   $46.50   $46.50  
  Purchase #3 $198.46   5.602%   $209.5777   $209.58   $209.60   $209.60  
  Purchase #4 $187.93   5.192%   $197.6873   $197.69   $197.70   $197.70  
  Purchase #5 $234.27   5.223%   $246.5059   $246.51   $246.50   $246.50  
  Purchase #6 $209.64   13.187%   $237.2852   $237.29   $237.30   $237.30  
  Purchase #7 $218.96   12.754%   $246.8862   $246.89   $246.90   $246.90  
  7 purchase totals = $1,153.16       $1,247.7136   $1,247.73   $1,247.75   $1,247.80