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	$237.84	4.205%	$247.8412	$247.84	$247.85	$247.80
Purchase #2	$126.42	11.743%	$141.2655	$141.27	$141.25	$141.30
Purchase #3	$153.76	7.583%	$165.4196	$165.42	$165.40	$165.40
Purchase #4	$247.28	13.437%	$280.507	$280.51	$280.50	$280.50
Purchase #5	$79.35	3.677%	$82.2677	$82.27	$82.25	$82.30
Purchase #6	$190.42	12.245%	$213.7369	$213.74	$213.75	$213.70
Purchase #7	$165.65	4.457%	$173.033	$173.03	$173.05	$173.00
7 purchase totals =	$1,200.72		$1,304.0709	$1,304.08	$1,304.05	$1,304.00