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	$232.64	6.299%	$247.294	$247.29	$247.30	$247.30
Purchase #2	$137.88	4.478%	$144.0543	$144.05	$144.05	$144.10
Purchase #3	$188.62	11.823%	$210.9205	$210.92	$210.90	$210.90
Purchase #4	$63.91	3.468%	$66.1264	$66.13	$66.15	$66.10
Purchase #5	$220.25	10.278%	$242.8873	$242.89	$242.90	$242.90
Purchase #6	$177.84	3.858%	$184.7011	$184.70	$184.70	$184.70
Purchase #7	$92.43	8.476%	$100.2644	$100.26	$100.25	$100.30
7 purchase totals =	$1,113.57		$1,196.2480	$1,196.24	$1,196.25	$1,196.30