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	$221.61	3.209%	$228.7215	$228.72	$228.70	$228.70
Purchase #2	$133.87	9.152%	$146.1218	$146.12	$146.10	$146.10
Purchase #3	$54.43	13.103%	$61.562	$61.56	$61.55	$61.60
Purchase #4	$75.83	3.450%	$78.4461	$78.45	$78.45	$78.40
Purchase #5	$248.41	9.383%	$271.7183	$271.72	$271.70	$271.70
Purchase #6	$206.41	13.516%	$234.3084	$234.31	$234.30	$234.30
Purchase #7	$15.76	10.241%	$17.374	$17.37	$17.35	$17.40
7 purchase totals =	$956.32		$1,038.2521	$1,038.25	$1,038.15	$1,038.20