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	$152.83	12.597%	$172.082	$172.08	$172.10	$172.10
Purchase #2	$103.55	7.471%	$111.2862	$111.29	$111.30	$111.30
Purchase #3	$87.97	8.332%	$95.2997	$95.30	$95.30	$95.30
Purchase #4	$166.26	13.223%	$188.2446	$188.24	$188.25	$188.20
Purchase #5	$100.70	3.832%	$104.5588	$104.56	$104.55	$104.60
Purchase #6	$139.53	8.789%	$151.7933	$151.79	$151.80	$151.80
Purchase #7	$228.34	4.385%	$238.3527	$238.35	$238.35	$238.40
7 purchase totals =	$979.18		$1,061.6173	$1,061.61	$1,061.65	$1,061.70