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	$202.93	6.737%	$216.6014	$216.60	$216.60	$216.60
Purchase #2	$88.91	13.323%	$100.7555	$100.76	$100.75	$100.80
Purchase #3	$221.79	13.111%	$250.8689	$250.87	$250.85	$250.90
Purchase #4	$242.25	4.303%	$252.674	$252.67	$252.65	$252.70
Purchase #5	$86.46	3.547%	$89.5267	$89.53	$89.55	$89.50
Purchase #6	$184.93	13.279%	$209.4869	$209.49	$209.50	$209.50
Purchase #7	$92.54	5.455%	$97.5881	$97.59	$97.60	$97.60
7 purchase totals =	$1,119.81		$1,217.5015	$1,217.51	$1,217.50	$1,217.60