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 $208.86   13.218%   $236.4671   $236.47   $236.45   $236.50  
  Purchase #2 $241.78   10.631%   $267.4836   $267.48   $267.50   $267.50  
  Purchase #3 $82.39   7.532%   $88.5956   $88.60   $88.60   $88.60  
  Purchase #4 $14.48   8.156%   $15.661   $15.66   $15.65   $15.70  
  Purchase #5 $166.37   4.161%   $173.2927   $173.29   $173.30   $173.30  
  Purchase #6 $10.93   3.515%   $11.3142   $11.31   $11.30   $11.30  
  Purchase #7 $222.96   9.520%   $244.1858   $244.19   $244.20   $244.20  
  7 purchase totals = $947.77       $1,037.0000   $1,037.00   $1,037.00   $1,037.10