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 $91.93   3.515%   $95.1613   $95.16   $95.15   $95.20  
  Purchase #2 $209.25   10.624%   $231.4807   $231.48   $231.50   $231.50  
  Purchase #3 $182.95   13.696%   $208.0068   $208.01   $208.00   $208.00  
  Purchase #4 $168.99   7.311%   $181.3449   $181.34   $181.35   $181.30  
  Purchase #5 $160.59   10.296%   $177.1243   $177.12   $177.10   $177.10  
  Purchase #6 $236.79   9.799%   $259.9931   $259.99   $260.00   $260.00  
  Purchase #7 $111.95   3.134%   $115.4585   $115.46   $115.45   $115.50  
  7 purchase totals = $1,162.45       $1,268.5696   $1,268.56   $1,268.55   $1,268.60