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 $224.37   5.553%   $236.8293   $236.83   $236.85   $236.80  
  Purchase #2 $84.83   10.554%   $93.783   $93.78   $93.80   $93.80  
  Purchase #3 $60.36   8.519%   $65.5021   $65.50   $65.50   $65.50  
  Purchase #4 $85.78   6.800%   $91.613   $91.61   $91.60   $91.60  
  Purchase #5 $147.38   11.251%   $163.9617   $163.96   $163.95   $164.00  
  Purchase #6 $161.93   6.197%   $171.9648   $171.96   $171.95   $172.00  
  Purchase #7 $189.25   11.349%   $210.728   $210.73   $210.75   $210.70  
  7 purchase totals = $953.90       $1,034.3819   $1,034.37   $1,034.40   $1,034.40