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 $196.87   8.566%   $213.7339   $213.73   $213.75   $213.70  
  Purchase #2 $119.62   5.323%   $125.9874   $125.99   $126.00   $126.00  
  Purchase #3 $228.25   11.500%   $254.4988   $254.50   $254.50   $254.50  
  Purchase #4 $91.35   11.868%   $102.1914   $102.19   $102.20   $102.20  
  Purchase #5 $31.98   8.593%   $34.728   $34.73   $34.75   $34.70  
  Purchase #6 $218.29   8.245%   $236.288   $236.29   $236.30   $236.30  
  Purchase #7 $162.71   8.503%   $176.5452   $176.55   $176.55   $176.50  
  7 purchase totals = $1,049.07       $1,143.9727   $1,143.98   $1,144.05   $1,143.90