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 $58.73   5.872%   $62.1786   $62.18   $62.20   $62.20  
  Purchase #2 $68.54   5.578%   $72.3632   $72.36   $72.35   $72.40  
  Purchase #3 $89.98   8.691%   $97.8002   $97.80   $97.80   $97.80  
  Purchase #4 $122.71   10.321%   $135.3749   $135.37   $135.35   $135.40  
  Purchase #5 $208.84   6.292%   $221.9802   $221.98   $222.00   $222.00  
  Purchase #6 $104.97   11.805%   $117.3617   $117.36   $117.35   $117.40  
  Purchase #7 $41.47   10.231%   $45.7128   $45.71   $45.70   $45.70  
  7 purchase totals = $695.24       $752.7716   $752.76   $752.75   $752.90