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	$102.33	8.630%	$111.1611	$111.16	$111.15	$111.20
Purchase #2	$159.92	11.616%	$178.4963	$178.50	$178.50	$178.50
Purchase #3	$138.95	3.479%	$143.7841	$143.78	$143.80	$143.80
Purchase #4	$53.62	12.122%	$60.1198	$60.12	$60.10	$60.10
Purchase #5	$122.73	6.184%	$130.3196	$130.32	$130.30	$130.30
Purchase #6	$48.43	13.244%	$54.8441	$54.84	$54.85	$54.80
Purchase #7	$71.53	6.856%	$76.4341	$76.43	$76.45	$76.40
7 purchase totals =	$697.51		$755.1591	$755.15	$755.15	$755.10