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 $222.73   8.629%   $241.9494   $241.95   $241.95   $241.90  
  Purchase #2 $237.97   13.361%   $269.7652   $269.77   $269.75   $269.80  
  Purchase #3 $142.94   3.751%   $148.3017   $148.30   $148.30   $148.30  
  Purchase #4 $191.35   4.116%   $199.226   $199.23   $199.25   $199.20  
  Purchase #5 $64.97   8.224%   $70.3131   $70.31   $70.30   $70.30  
  Purchase #6 $76.27   13.580%   $86.6275   $86.63   $86.65   $86.60  
  Purchase #7 $7.51   11.452%   $8.37   $8.37   $8.35   $8.40  
  7 purchase totals = $943.74       $1,024.5529   $1,024.56   $1,024.55   $1,024.50