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	$159.69	7.125%	$171.0679	$171.07	$171.05	$171.10
Purchase #2	$36.99	7.847%	$39.8926	$39.89	$39.90	$39.90
Purchase #3	$112.32	13.234%	$127.1844	$127.18	$127.20	$127.20
Purchase #4	$238.75	5.201%	$251.1674	$251.17	$251.15	$251.20
Purchase #5	$94.74	5.728%	$100.1667	$100.17	$100.15	$100.20
Purchase #6	$126.71	11.525%	$141.3133	$141.31	$141.30	$141.30
Purchase #7	$223.92	10.160%	$246.6703	$246.67	$246.65	$246.70
7 purchase totals =	$993.12		$1,077.4626	$1,077.46	$1,077.40	$1,077.60