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	$143.29	9.769%	$157.288	$157.29	$157.30	$157.30
Purchase #2	$185.42	7.139%	$198.6571	$198.66	$198.65	$198.70
Purchase #3	$242.33	5.493%	$255.6412	$255.64	$255.65	$255.60
Purchase #4	$80.82	8.211%	$87.4561	$87.46	$87.45	$87.50
Purchase #5	$78.60	12.780%	$88.6451	$88.65	$88.65	$88.60
Purchase #6	$247.81	4.305%	$258.4782	$258.48	$258.50	$258.50
Purchase #7	$88.68	13.834%	$100.948	$100.95	$100.95	$100.90
7 purchase totals =	$1,066.95		$1,147.1137	$1,147.13	$1,147.15	$1,147.10