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 $214.39   13.465%   $243.2576   $243.26   $243.25   $243.30  
  Purchase #2 $48.79   7.631%   $52.5132   $52.51   $52.50   $52.50  
  Purchase #3 $207.84   9.724%   $228.0504   $228.05   $228.05   $228.10  
  Purchase #4 $173.40   13.777%   $197.2893   $197.29   $197.30   $197.30  
  Purchase #5 $86.81   6.385%   $92.3528   $92.35   $92.35   $92.40  
  Purchase #6 $185.63   5.215%   $195.3106   $195.31   $195.30   $195.30  
  Purchase #7 $184.88   7.350%   $198.4687   $198.47   $198.45   $198.50  
  7 purchase totals = $1,101.74       $1,207.2426   $1,207.24   $1,207.20   $1,207.40