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 $162.92   7.527%   $175.183   $175.18   $175.20   $175.20  
  Purchase #2 $113.66   10.497%   $125.5909   $125.59   $125.60   $125.60  
  Purchase #3 $70.47   9.873%   $77.4275   $77.43   $77.45   $77.40  
  Purchase #4 $123.98   9.244%   $135.4407   $135.44   $135.45   $135.40  
  Purchase #5 $237.85   8.799%   $258.7784   $258.78   $258.80   $258.80  
  Purchase #6 $48.26   6.792%   $51.5378   $51.54   $51.55   $51.50  
  Purchase #7 $115.89   11.126%   $128.7839   $128.78   $128.80   $128.80  
  7 purchase totals = $873.03       $952.7422   $952.74   $952.85   $952.70