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 $32.86   4.165%   $34.2286   $34.23   $34.25   $34.20  
  Purchase #2 $86.67   6.828%   $92.5878   $92.59   $92.60   $92.60  
  Purchase #3 $195.87   3.811%   $203.3346   $203.33   $203.35   $203.30  
  Purchase #4 $163.45   10.750%   $181.0209   $181.02   $181.00   $181.00  
  Purchase #5 $161.51   4.862%   $169.3626   $169.36   $169.35   $169.40  
  Purchase #6 $187.58   11.509%   $209.1686   $209.17   $209.15   $209.20  
  Purchase #7 $250.64   5.758%   $265.0719   $265.07   $265.05   $265.10  
  7 purchase totals = $1,078.58       $1,154.7750   $1,154.77   $1,154.75   $1,154.80