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 $203.76   5.210%   $214.3759   $214.38   $214.40   $214.40  
  Purchase #2 $160.42   10.157%   $176.7139   $176.71   $176.70   $176.70  
  Purchase #3 $206.85   12.379%   $232.456   $232.46   $232.45   $232.50  
  Purchase #4 $7.29   6.109%   $7.7353   $7.74   $7.75   $7.70  
  Purchase #5 $86.67   6.567%   $92.3616   $92.36   $92.35   $92.40  
  Purchase #6 $97.56   3.647%   $101.118   $101.12   $101.10   $101.10  
  Purchase #7 $188.90   11.131%   $209.9265   $209.93   $209.95   $209.90  
  7 purchase totals = $951.45       $1,034.6872   $1,034.70   $1,034.70   $1,034.70