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	$215.74	9.531%	$236.3022	$236.30	$236.30	$236.30
Purchase #2	$26.35	8.638%	$28.6261	$28.63	$28.65	$28.60
Purchase #3	$67.60	4.856%	$70.8827	$70.88	$70.90	$70.90
Purchase #4	$99.27	11.815%	$110.9988	$111.00	$111.00	$111.00
Purchase #5	$209.95	5.845%	$222.2216	$222.22	$222.20	$222.20
Purchase #6	$154.76	12.171%	$173.5958	$173.60	$173.60	$173.60
Purchase #7	$54.89	12.371%	$61.6804	$61.68	$61.70	$61.70
7 purchase totals =	$828.56		$904.3076	$904.31	$904.35	$904.30