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 $114.98   3.478%   $118.979   $118.98   $119.00   $119.00  
  Purchase #2 $244.78   5.748%   $258.85   $258.85   $258.85   $258.90  
  Purchase #3 $93.88   9.652%   $102.9413   $102.94   $102.95   $102.90  
  Purchase #4 $51.42   13.844%   $58.5386   $58.54   $58.55   $58.50  
  Purchase #5 $248.63   3.359%   $256.9815   $256.98   $257.00   $257.00  
  Purchase #6 $23.39   9.407%   $25.5903   $25.59   $25.60   $25.60  
  Purchase #7 $96.97   9.807%   $106.4798   $106.48   $106.50   $106.50  
  7 purchase totals = $874.05       $928.3605   $928.36   $928.45   $928.40