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	$141.92	3.221%	$146.4912	$146.49	$146.50	$146.50
Purchase #2	$105.75	5.557%	$111.6265	$111.63	$111.65	$111.60
Purchase #3	$172.85	4.657%	$180.8996	$180.90	$180.90	$180.90
Purchase #4	$76.74	4.665%	$80.3199	$80.32	$80.30	$80.30
Purchase #5	$98.68	11.583%	$110.1101	$110.11	$110.10	$110.10
Purchase #6	$212.44	13.782%	$241.7185	$241.72	$241.70	$241.70
Purchase #7	$227.66	3.388%	$235.3731	$235.37	$235.35	$235.40
7 purchase totals =	$1,036.04		$1,106.5389	$1,106.54	$1,106.50	$1,106.50