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 $233.63   12.542%   $262.9319   $262.93   $262.95   $262.90  
  Purchase #2 $242.93   6.626%   $259.0265   $259.03   $259.05   $259.00  
  Purchase #3 $232.43   13.532%   $263.8824   $263.88   $263.90   $263.90  
  Purchase #4 $182.40   8.156%   $197.2765   $197.28   $197.30   $197.30  
  Purchase #5 $29.59   7.297%   $31.7492   $31.75   $31.75   $31.70  
  Purchase #6 $227.43   3.319%   $234.9784   $234.98   $235.00   $235.00  
  Purchase #7 $215.97   13.255%   $244.5968   $244.60   $244.60   $244.60  
  7 purchase totals = $1,364.38       $1,494.4417   $1,494.45   $1,494.55   $1,494.40