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 $55.55   11.514%   $61.946   $61.95   $61.95   $61.90  
  Purchase #2 $173.78   9.661%   $190.5689   $190.57   $190.55   $190.60  
  Purchase #3 $195.76   3.817%   $203.2322   $203.23   $203.25   $203.20  
  Purchase #4 $202.76   4.349%   $211.578   $211.58   $211.60   $211.60  
  Purchase #5 $110.61   13.381%   $125.4107   $125.41   $125.40   $125.40  
  Purchase #6 $18.42   13.216%   $20.8544   $20.85   $20.85   $20.90  
  Purchase #7 $106.26   12.809%   $119.8708   $119.87   $119.85   $119.90  
  7 purchase totals = $863.14       $933.4610   $933.46   $933.45   $933.50