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	$106.38	4.781%	$111.466	$111.47	$111.45	$111.50
Purchase #2	$109.59	8.621%	$119.0378	$119.04	$119.05	$119.00
Purchase #3	$237.80	9.390%	$260.1294	$260.13	$260.15	$260.10
Purchase #4	$141.91	5.823%	$150.1734	$150.17	$150.15	$150.20
Purchase #5	$176.39	8.778%	$191.8735	$191.87	$191.85	$191.90
Purchase #6	$161.26	6.741%	$172.1305	$172.13	$172.15	$172.10
Purchase #7	$156.82	8.613%	$170.3269	$170.33	$170.35	$170.30
7 purchase totals =	$1,090.15		$1,175.1375	$1,175.14	$1,175.15	$1,175.10