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 $181.36   8.444%   $196.674   $196.67   $196.65   $196.70  
  Purchase #2 $52.63   13.141%   $59.5461   $59.55   $59.55   $59.50  
  Purchase #3 $14.86   13.659%   $16.8897   $16.89   $16.90   $16.90  
  Purchase #4 $212.33   13.141%   $240.2323   $240.23   $240.25   $240.20  
  Purchase #5 $64.60   3.179%   $66.6536   $66.65   $66.65   $66.70  
  Purchase #6 $194.74   11.810%   $217.7388   $217.74   $217.75   $217.70  
  Purchase #7 $31.44   8.346%   $34.064   $34.06   $34.05   $34.10  
  7 purchase totals = $751.96       $831.7985   $831.79   $831.80   $831.80