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	$60.83	10.745%	$67.3662	$67.37	$67.35	$67.40
Purchase #2	$133.59	7.242%	$143.2646	$143.26	$143.25	$143.30
Purchase #3	$35.34	6.698%	$37.7071	$37.71	$37.70	$37.70
Purchase #4	$236.33	5.439%	$249.184	$249.18	$249.20	$249.20
Purchase #5	$147.39	11.675%	$164.5978	$164.60	$164.60	$164.60
Purchase #6	$195.69	12.652%	$220.4487	$220.45	$220.45	$220.40
Purchase #7	$35.40	6.218%	$37.6012	$37.60	$37.60	$37.60
7 purchase totals =	$844.57		$920.1696	$920.17	$920.15	$920.20