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	$60.93	9.575%	$66.764	$66.76	$66.75	$66.80
Purchase #2	$56.86	5.331%	$59.8912	$59.89	$59.90	$59.90
Purchase #3	$193.29	4.428%	$201.8489	$201.85	$201.85	$201.80
Purchase #4	$153.50	3.677%	$159.1442	$159.14	$159.15	$159.10
Purchase #5	$233.98	8.413%	$253.6647	$253.66	$253.65	$253.70
Purchase #6	$159.89	7.580%	$172.0097	$172.01	$172.00	$172.00
Purchase #7	$61.31	6.829%	$65.4969	$65.50	$65.50	$65.50
7 purchase totals =	$919.76		$978.8196	$978.81	$978.80	$978.80