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 $228.64   5.743%   $241.7708   $241.77   $241.75   $241.80  
  Purchase #2 $245.94   6.303%   $261.4416   $261.44   $261.45   $261.40  
  Purchase #3 $150.83   9.468%   $165.1106   $165.11   $165.10   $165.10  
  Purchase #4 $44.86   8.579%   $48.7085   $48.71   $48.70   $48.70  
  Purchase #5 $241.85   5.140%   $254.2811   $254.28   $254.30   $254.30  
  Purchase #6 $125.55   6.337%   $133.5061   $133.51   $133.50   $133.50  
  Purchase #7 $68.40   4.571%   $71.5266   $71.53   $71.55   $71.50  
  7 purchase totals = $1,106.07       $1,176.3453   $1,176.35   $1,176.35   $1,176.30