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 $193.77   8.105%   $209.4751   $209.48   $209.50   $209.50  
  Purchase #2 $200.30   8.653%   $217.632   $217.63   $217.65   $217.60  
  Purchase #3 $91.39   8.254%   $98.9333   $98.93   $98.95   $98.90  
  Purchase #4 $191.97   8.244%   $207.796   $207.80   $207.80   $207.80  
  Purchase #5 $77.30   6.539%   $82.3546   $82.35   $82.35   $82.40  
  Purchase #6 $216.70   12.850%   $244.546   $244.55   $244.55   $244.50  
  Purchase #7 $99.55   5.314%   $104.8401   $104.84   $104.85   $104.80  
  7 purchase totals = $1,070.98       $1,165.5771   $1,165.58   $1,165.65   $1,165.50