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 $227.46   3.429%   $235.2596   $235.26   $235.25   $235.30  
  Purchase #2 $181.45   6.786%   $193.7632   $193.76   $193.75   $193.80  
  Purchase #3 $178.62   5.575%   $188.5781   $188.58   $188.60   $188.60  
  Purchase #4 $60.80   3.837%   $63.1329   $63.13   $63.15   $63.10  
  Purchase #5 $231.66   4.159%   $241.2947   $241.29   $241.30   $241.30  
  Purchase #6 $85.80   10.293%   $94.6314   $94.63   $94.65   $94.60  
  Purchase #7 $49.46   4.764%   $51.8163   $51.82   $51.80   $51.80  
  7 purchase totals = $1,015.25       $1,068.4762   $1,068.47   $1,068.50   $1,068.50