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 $67.51   13.414%   $76.5658   $76.57   $76.55   $76.60  
  Purchase #2 $53.96   11.831%   $60.344   $60.34   $60.35   $60.30  
  Purchase #3 $218.63   9.734%   $239.9114   $239.91   $239.90   $239.90  
  Purchase #4 $182.26   9.212%   $199.0498   $199.05   $199.05   $199.00  
  Purchase #5 $161.90   7.828%   $174.5735   $174.57   $174.55   $174.60  
  Purchase #6 $170.48   12.400%   $191.6195   $191.62   $191.60   $191.60  
  Purchase #7 $185.71   8.402%   $201.3134   $201.31   $201.30   $201.30  
  7 purchase totals = $1,040.45       $1,143.3774   $1,143.37   $1,143.30   $1,143.30