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	$161.59	7.766%	$174.1391	$174.14	$174.15	$174.10
Purchase #2	$58.92	3.709%	$61.1053	$61.11	$61.10	$61.10
Purchase #3	$66.27	9.656%	$72.669	$72.67	$72.65	$72.70
Purchase #4	$118.82	6.803%	$126.9033	$126.90	$126.90	$126.90
Purchase #5	$99.86	5.608%	$105.4601	$105.46	$105.45	$105.50
Purchase #6	$235.87	7.134%	$252.697	$252.70	$252.70	$252.70
Purchase #7	$224.89	5.565%	$237.4051	$237.41	$237.40	$237.40
7 purchase totals =	$966.22		$1,030.3789	$1,030.39	$1,030.35	$1,030.40