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 $169.44   3.354%   $175.123   $175.12   $175.10   $175.10  
  Purchase #2 $181.48   8.378%   $196.6844   $196.68   $196.70   $196.70  
  Purchase #3 $108.61   10.464%   $119.975   $119.98   $120.00   $120.00  
  Purchase #4 $52.68   13.375%   $59.726   $59.73   $59.75   $59.70  
  Purchase #5 $54.70   13.105%   $61.8684   $61.87   $61.85   $61.90  
  Purchase #6 $65.48   6.820%   $69.9457   $69.95   $69.95   $69.90  
  Purchase #7 $80.74   8.586%   $87.6723   $87.67   $87.65   $87.70  
  7 purchase totals = $713.13       $770.9948   $771.00   $771.00   $771.00