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	$95.88	12.696%	$108.0529	$108.05	$108.05	$108.10
Purchase #2	$218.83	11.551%	$244.1071	$244.11	$244.10	$244.10
Purchase #3	$172.58	8.595%	$187.4133	$187.41	$187.40	$187.40
Purchase #4	$231.73	4.648%	$242.5008	$242.50	$242.50	$242.50
Purchase #5	$97.94	13.695%	$111.3529	$111.35	$111.35	$111.40
Purchase #6	$200.58	12.229%	$225.1089	$225.11	$225.10	$225.10
Purchase #7	$38.26	6.420%	$40.7163	$40.72	$40.70	$40.70
7 purchase totals =	$1,055.80		$1,159.2522	$1,159.25	$1,159.20	$1,159.30