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	$219.80	9.698%	$241.1162	$241.12	$241.10	$241.10
Purchase #2	$20.89	6.522%	$22.2524	$22.25	$22.25	$22.30
Purchase #3	$229.56	11.565%	$256.1086	$256.11	$256.10	$256.10
Purchase #4	$78.88	5.753%	$83.418	$83.42	$83.40	$83.40
Purchase #5	$61.53	13.485%	$69.8273	$69.83	$69.85	$69.80
Purchase #6	$40.41	4.479%	$42.22	$42.22	$42.20	$42.20
Purchase #7	$130.96	7.103%	$140.2621	$140.26	$140.25	$140.30
7 purchase totals =	$782.03		$855.2046	$855.21	$855.15	$855.20