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 $212.41   5.737%   $224.596   $224.60   $224.60   $224.60  
  Purchase #2 $55.88   10.757%   $61.891   $61.89   $61.90   $61.90  
  Purchase #3 $6.95   13.686%   $7.9012   $7.90   $7.90   $7.90  
  Purchase #4 $88.61   6.418%   $94.297   $94.30   $94.30   $94.30  
  Purchase #5 $132.39   7.349%   $142.1193   $142.12   $142.10   $142.10  
  Purchase #6 $37.44   5.729%   $39.5849   $39.58   $39.60   $39.60  
  Purchase #7 $161.27   11.750%   $180.2192   $180.22   $180.20   $180.20  
  7 purchase totals = $694.95       $750.6086   $750.61   $750.60   $750.60