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 $82.88   11.793%   $92.654   $92.65   $92.65   $92.70  
  Purchase #2 $60.78   4.825%   $63.7126   $63.71   $63.70   $63.70  
  Purchase #3 $247.87   6.257%   $263.3792   $263.38   $263.40   $263.40  
  Purchase #4 $14.42   9.783%   $15.8307   $15.83   $15.85   $15.80  
  Purchase #5 $113.35   4.634%   $118.6026   $118.60   $118.60   $118.60  
  Purchase #6 $241.56   6.819%   $258.032   $258.03   $258.05   $258.00  
  Purchase #7 $19.67   5.829%   $20.8166   $20.82   $20.80   $20.80  
  7 purchase totals = $780.53       $833.0277   $833.02   $833.05   $833.00