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 $208.74   8.652%   $226.8002   $226.80   $226.80   $226.80  
  Purchase #2 $177.86   7.522%   $191.2386   $191.24   $191.25   $191.20  
  Purchase #3 $51.26   11.344%   $57.0749   $57.07   $57.05   $57.10  
  Purchase #4 $157.87   11.448%   $175.943   $175.94   $175.95   $175.90  
  Purchase #5 $247.85   7.350%   $266.067   $266.07   $266.05   $266.10  
  Purchase #6 $161.67   7.488%   $173.7758   $173.78   $173.80   $173.80  
  Purchase #7 $196.51   10.809%   $217.7508   $217.75   $217.75   $217.80  
  7 purchase totals = $1,201.76       $1,308.6503   $1,308.65   $1,308.65   $1,308.70