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	$125.51	8.850%	$136.6176	$136.62	$136.60	$136.60
Purchase #2	$126.29	4.247%	$131.6535	$131.65	$131.65	$131.70
Purchase #3	$158.60	13.472%	$179.9666	$179.97	$179.95	$180.00
Purchase #4	$149.98	11.292%	$166.9157	$166.92	$166.90	$166.90
Purchase #5	$134.26	13.199%	$151.981	$151.98	$152.00	$152.00
Purchase #6	$87.70	13.566%	$99.5974	$99.60	$99.60	$99.60
Purchase #7	$173.69	9.396%	$190.0099	$190.01	$190.00	$190.00
7 purchase totals =	$956.03		$1,056.7417	$1,056.75	$1,056.70	$1,056.80