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 $67.85   12.259%   $76.1677   $76.17   $76.15   $76.20  
  Purchase #2 $213.57   9.450%   $233.7524   $233.75   $233.75   $233.80  
  Purchase #3 $132.38   3.422%   $136.91   $136.91   $136.90   $136.90  
  Purchase #4 $168.27   13.255%   $190.5742   $190.57   $190.55   $190.60  
  Purchase #5 $99.92   7.502%   $107.416   $107.42   $107.40   $107.40  
  Purchase #6 $207.45   8.443%   $224.965   $224.97   $224.95   $225.00  
  Purchase #7 $142.69   3.460%   $147.6271   $147.63   $147.65   $147.60  
  7 purchase totals = $1,032.13       $1,117.4124   $1,117.42   $1,117.35   $1,117.50