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 $199.51   7.520%   $214.5132   $214.51   $214.50   $214.50  
  Purchase #2 $44.57   8.188%   $48.2194   $48.22   $48.20   $48.20  
  Purchase #3 $24.42   6.266%   $25.9502   $25.95   $25.95   $26.00  
  Purchase #4 $133.82   6.612%   $142.6682   $142.67   $142.65   $142.70  
  Purchase #5 $180.76   12.482%   $203.3225   $203.32   $203.30   $203.30  
  Purchase #6 $176.86   13.254%   $200.301   $200.30   $200.30   $200.30  
  Purchase #7 $68.62   8.348%   $74.3484   $74.35   $74.35   $74.30  
  7 purchase totals = $828.56       $909.3229   $909.32   $909.25   $909.30