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	$151.27	9.782%	$166.0672	$166.07	$166.05	$166.10
Purchase #2	$246.39	13.129%	$278.7385	$278.74	$278.75	$278.70
Purchase #3	$241.95	12.239%	$271.5623	$271.56	$271.55	$271.60
Purchase #4	$244.56	7.279%	$262.3615	$262.36	$262.35	$262.40
Purchase #5	$89.60	6.809%	$95.7009	$95.70	$95.70	$95.70
Purchase #6	$31.76	5.437%	$33.4868	$33.49	$33.50	$33.50
Purchase #7	$185.64	5.834%	$196.4702	$196.47	$196.45	$196.50
7 purchase totals =	$1,191.17		$1,304.3874	$1,304.39	$1,304.35	$1,304.50