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 $30.37   8.482%   $32.946   $32.95   $32.95   $32.90  
  Purchase #2 $45.62   5.106%   $47.9494   $47.95   $47.95   $47.90  
  Purchase #3 $209.46   8.376%   $227.0044   $227.00   $227.00   $227.00  
  Purchase #4 $250.54   11.623%   $279.6603   $279.66   $279.65   $279.70  
  Purchase #5 $196.43   5.518%   $207.269   $207.27   $207.25   $207.30  
  Purchase #6 $180.52   9.525%   $197.7145   $197.71   $197.70   $197.70  
  Purchase #7 $101.48   9.673%   $111.2962   $111.30   $111.30   $111.30  
  7 purchase totals = $1,014.42       $1,103.8398   $1,103.84   $1,103.80   $1,103.80