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	$100.30	10.738%	$111.0702	$111.07	$111.05	$111.10
Purchase #2	$10.91	5.561%	$11.5167	$11.52	$11.50	$11.50
Purchase #3	$57.41	11.703%	$64.1287	$64.13	$64.15	$64.10
Purchase #4	$120.35	8.611%	$130.7133	$130.71	$130.70	$130.70
Purchase #5	$94.60	9.340%	$103.4356	$103.44	$103.45	$103.40
Purchase #6	$106.62	5.421%	$112.3999	$112.40	$112.40	$112.40
Purchase #7	$86.64	8.492%	$93.9975	$94.00	$94.00	$94.00
7 purchase totals =	$576.83		$627.2619	$627.27	$627.25	$627.20