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	$209.76	13.546%	$238.1741	$238.17	$238.15	$238.20
Purchase #2	$97.74	4.204%	$101.849	$101.85	$101.85	$101.80
Purchase #3	$17.29	13.244%	$19.5799	$19.58	$19.60	$19.60
Purchase #4	$89.28	7.364%	$95.8546	$95.85	$95.85	$95.90
Purchase #5	$161.41	5.179%	$169.7694	$169.77	$169.75	$169.80
Purchase #6	$146.82	3.253%	$151.5961	$151.60	$151.60	$151.60
Purchase #7	$243.91	11.621%	$272.2548	$272.25	$272.25	$272.30
7 purchase totals =	$966.21		$1,049.0779	$1,049.07	$1,049.05	$1,049.20