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	$212.44	13.698%	$241.54	$241.54	$241.55	$241.50
Purchase #2	$151.46	12.425%	$170.2789	$170.28	$170.30	$170.30
Purchase #3	$129.79	7.815%	$139.9331	$139.93	$139.95	$139.90
Purchase #4	$66.87	6.525%	$71.2333	$71.23	$71.25	$71.20
Purchase #5	$221.92	9.417%	$242.8182	$242.82	$242.80	$242.80
Purchase #6	$166.93	11.305%	$185.8014	$185.80	$185.80	$185.80
Purchase #7	$242.71	13.647%	$275.8326	$275.83	$275.85	$275.80
7 purchase totals =	$1,192.12		$1,327.4375	$1,327.43	$1,327.50	$1,327.30