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 $92.72   3.654%   $96.108   $96.11   $96.10   $96.10  
  Purchase #2 $117.71   8.545%   $127.7683   $127.77   $127.75   $127.80  
  Purchase #3 $245.43   8.181%   $265.5086   $265.51   $265.50   $265.50  
  Purchase #4 $185.88   4.103%   $193.5067   $193.51   $193.50   $193.50  
  Purchase #5 $21.55   6.565%   $22.9648   $22.96   $22.95   $23.00  
  Purchase #6 $249.70   11.339%   $278.0135   $278.01   $278.00   $278.00  
  Purchase #7 $131.54   8.240%   $142.3789   $142.38   $142.40   $142.40  
  7 purchase totals = $1,044.53       $1,126.2488   $1,126.25   $1,126.20   $1,126.30