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	$215.71	3.142%	$222.4876	$222.49	$222.50	$222.50
Purchase #2	$196.57	13.802%	$223.7006	$223.70	$223.70	$223.70
Purchase #3	$34.75	8.506%	$37.7058	$37.71	$37.70	$37.70
Purchase #4	$91.43	9.449%	$100.0692	$100.07	$100.05	$100.10
Purchase #5	$5.51	3.640%	$5.7106	$5.71	$5.70	$5.70
Purchase #6	$144.38	6.485%	$153.743	$153.74	$153.75	$153.70
Purchase #7	$67.66	5.788%	$71.5762	$71.58	$71.60	$71.60
7 purchase totals =	$756.01		$814.9930	$815.00	$815.00	$815.00