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	$153.66	12.511%	$172.8844	$172.88	$172.90	$172.90
Purchase #2	$228.78	5.764%	$241.9669	$241.97	$241.95	$242.00
Purchase #3	$247.42	12.796%	$279.0799	$279.08	$279.10	$279.10
Purchase #4	$188.45	11.195%	$209.547	$209.55	$209.55	$209.50
Purchase #5	$219.81	5.496%	$231.8908	$231.89	$231.90	$231.90
Purchase #6	$217.41	5.380%	$229.1067	$229.11	$229.10	$229.10
Purchase #7	$92.93	11.533%	$103.6476	$103.65	$103.65	$103.60
7 purchase totals =	$1,348.46		$1,468.1233	$1,468.13	$1,468.15	$1,468.10