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	$40.63	7.568%	$43.7049	$43.70	$43.70	$43.70
Purchase #2	$111.85	13.649%	$127.1164	$127.12	$127.10	$127.10
Purchase #3	$68.42	3.529%	$70.8345	$70.83	$70.85	$70.80
Purchase #4	$134.89	3.243%	$139.2645	$139.26	$139.25	$139.30
Purchase #5	$48.64	4.342%	$50.7519	$50.75	$50.75	$50.80
Purchase #6	$221.31	4.493%	$231.2535	$231.25	$231.25	$231.30
Purchase #7	$78.92	5.644%	$83.3742	$83.37	$83.35	$83.40
7 purchase totals =	$704.66		$746.2999	$746.28	$746.25	$746.40