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	$242.97	6.424%	$258.5784	$258.58	$258.60	$258.60
Purchase #2	$10.73	3.802%	$11.138	$11.14	$11.15	$11.10
Purchase #3	$216.75	11.740%	$242.1965	$242.20	$242.20	$242.20
Purchase #4	$56.88	13.784%	$64.7203	$64.72	$64.70	$64.70
Purchase #5	$179.86	4.678%	$188.2739	$188.27	$188.25	$188.30
Purchase #6	$128.71	13.822%	$146.5003	$146.50	$146.50	$146.50
Purchase #7	$127.52	9.296%	$139.3743	$139.37	$139.35	$139.40
7 purchase totals =	$963.42		$1,050.7817	$1,050.78	$1,050.75	$1,050.80