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 $104.88   7.386%   $112.6264   $112.63   $112.65   $112.60  
  Purchase #2 $214.82   10.117%   $236.5533   $236.55   $236.55   $236.60  
  Purchase #3 $158.87   9.849%   $174.5171   $174.52   $174.50   $174.50  
  Purchase #4 $219.46   11.726%   $245.1939   $245.19   $245.20   $245.20  
  Purchase #5 $118.70   4.428%   $123.956   $123.96   $123.95   $124.00  
  Purchase #6 $163.27   4.752%   $171.0286   $171.03   $171.05   $171.00  
  Purchase #7 $7.51   8.190%   $8.1251   $8.13   $8.15   $8.10  
  7 purchase totals = $987.51       $1,072.0004   $1,072.01   $1,072.05   $1,072.00