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 $248.39   5.775%   $262.7345   $262.73   $262.75   $262.70  
  Purchase #2 $174.30   9.850%   $191.4686   $191.47   $191.45   $191.50  
  Purchase #3 $134.43   10.844%   $149.0076   $149.01   $149.00   $149.00  
  Purchase #4 $78.94   9.127%   $86.1449   $86.14   $86.15   $86.10  
  Purchase #5 $206.62   8.731%   $224.66   $224.66   $224.65   $224.70  
  Purchase #6 $96.43   6.625%   $102.8185   $102.82   $102.80   $102.80  
  Purchase #7 $141.56   12.734%   $159.5863   $159.59   $159.60   $159.60  
  7 purchase totals = $1,080.67       $1,176.4204   $1,176.42   $1,176.40   $1,176.40