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 $54.84   4.785%   $57.4641   $57.46   $57.45   $57.50  
  Purchase #2 $126.84   7.421%   $136.2528   $136.25   $136.25   $136.30  
  Purchase #3 $83.27   5.519%   $87.8657   $87.87   $87.85   $87.90  
  Purchase #4 $201.85   5.683%   $213.3211   $213.32   $213.30   $213.30  
  Purchase #5 $233.71   12.370%   $262.6199   $262.62   $262.60   $262.60  
  Purchase #6 $111.25   8.641%   $120.8631   $120.86   $120.85   $120.90  
  Purchase #7 $209.61   11.563%   $233.8472   $233.85   $233.85   $233.80  
  7 purchase totals = $1,021.37       $1,112.2339   $1,112.23   $1,112.15   $1,112.30