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 $108.74   4.802%   $113.9617   $113.96   $113.95   $114.00  
  Purchase #2 $44.30   6.552%   $47.2025   $47.20   $47.20   $47.20  
  Purchase #3 $213.61   9.790%   $234.5224   $234.52   $234.50   $234.50  
  Purchase #4 $27.67   9.266%   $30.2339   $30.23   $30.25   $30.20  
  Purchase #5 $247.84   13.457%   $281.1918   $281.19   $281.20   $281.20  
  Purchase #6 $110.95   6.322%   $117.9643   $117.96   $117.95   $118.00  
  Purchase #7 $215.44   9.307%   $235.491   $235.49   $235.50   $235.50  
  7 purchase totals = $968.55       $1,060.5676   $1,060.55   $1,060.55   $1,060.60