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	$218.40	11.502%	$243.5204	$243.52	$243.50	$243.50
Purchase #2	$209.72	4.612%	$219.3923	$219.39	$219.40	$219.40
Purchase #3	$205.48	12.205%	$230.5588	$230.56	$230.55	$230.60
Purchase #4	$167.82	7.655%	$180.6666	$180.67	$180.65	$180.70
Purchase #5	$165.34	4.255%	$172.3752	$172.38	$172.40	$172.40
Purchase #6	$53.89	13.732%	$61.2902	$61.29	$61.30	$61.30
Purchase #7	$147.57	7.156%	$158.1301	$158.13	$158.15	$158.10
7 purchase totals =	$1,168.22		$1,265.9336	$1,265.94	$1,265.95	$1,266.00