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 $86.82   8.826%   $94.4827   $94.48   $94.50   $94.50  
  Purchase #2 $219.49   3.808%   $227.8482   $227.85   $227.85   $227.80  
  Purchase #3 $99.85   11.304%   $111.137   $111.14   $111.15   $111.10  
  Purchase #4 $209.89   3.662%   $217.5762   $217.58   $217.60   $217.60  
  Purchase #5 $197.79   5.427%   $208.5241   $208.52   $208.50   $208.50  
  Purchase #6 $229.85   8.463%   $249.3022   $249.30   $249.30   $249.30  
  Purchase #7 $109.92   8.236%   $118.973   $118.97   $118.95   $119.00  
  7 purchase totals = $1,153.61       $1,227.8434   $1,227.84   $1,227.85   $1,227.80