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 $101.86   4.713%   $106.6607   $106.66   $106.65   $106.70  
  Purchase #2 $229.44   9.494%   $251.223   $251.22   $251.20   $251.20  
  Purchase #3 $78.79   8.598%   $85.5644   $85.56   $85.55   $85.60  
  Purchase #4 $168.36   6.708%   $179.6536   $179.65   $179.65   $179.70  
  Purchase #5 $121.65   3.822%   $126.2995   $126.30   $126.30   $126.30  
  Purchase #6 $108.80   11.591%   $121.411   $121.41   $121.40   $121.40  
  Purchase #7 $75.99   11.743%   $84.9135   $84.91   $84.90   $84.90  
  7 purchase totals = $884.89       $955.7257   $955.71   $955.65   $955.80