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	$89.38	5.610%	$94.3942	$94.39	$94.40	$94.40
Purchase #2	$182.92	11.745%	$204.404	$204.40	$204.40	$204.40
Purchase #3	$100.67	11.162%	$111.9068	$111.91	$111.90	$111.90
Purchase #4	$138.34	5.180%	$145.506	$145.51	$145.50	$145.50
Purchase #5	$112.49	5.742%	$118.9492	$118.95	$118.95	$118.90
Purchase #6	$44.82	11.402%	$49.9304	$49.93	$49.95	$49.90
Purchase #7	$134.60	12.237%	$151.071	$151.07	$151.05	$151.10
7 purchase totals =	$803.22		$876.1616	$876.16	$876.15	$876.10