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 $41.60   5.348%   $43.8248   $43.82   $43.80   $43.80  
  Purchase #2 $146.92   10.277%   $162.019   $162.02   $162.00   $162.00  
  Purchase #3 $39.71   3.114%   $40.9466   $40.95   $40.95   $40.90  
  Purchase #4 $200.72   5.560%   $211.88   $211.88   $211.90   $211.90  
  Purchase #5 $157.99   11.182%   $175.6564   $175.66   $175.65   $175.70  
  Purchase #6 $148.73   13.586%   $168.9365   $168.94   $168.95   $168.90  
  Purchase #7 $243.45   7.406%   $261.4799   $261.48   $261.50   $261.50  
  7 purchase totals = $979.12       $1,064.7432   $1,064.75   $1,064.75   $1,064.70