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 $231.94   9.590%   $254.183   $254.18   $254.20   $254.20  
  Purchase #2 $205.51   3.829%   $213.379   $213.38   $213.40   $213.40  
  Purchase #3 $200.73   3.735%   $208.2273   $208.23   $208.25   $208.20  
  Purchase #4 $161.75   5.111%   $170.017   $170.02   $170.00   $170.00  
  Purchase #5 $215.58   9.282%   $235.5901   $235.59   $235.60   $235.60  
  Purchase #6 $57.93   7.811%   $62.4549   $62.45   $62.45   $62.50  
  Purchase #7 $37.85   8.601%   $41.1055   $41.11   $41.10   $41.10  
  7 purchase totals = $1,111.29       $1,184.9568   $1,184.96   $1,185.00   $1,185.00