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	$195.72	11.272%	$217.7816	$217.78	$217.80	$217.80
Purchase #2	$44.79	4.444%	$46.7805	$46.78	$46.80	$46.80
Purchase #3	$154.92	6.735%	$165.3539	$165.35	$165.35	$165.40
Purchase #4	$172.90	10.763%	$191.5092	$191.51	$191.50	$191.50
Purchase #5	$8.64	13.684%	$9.8223	$9.82	$9.80	$9.80
Purchase #6	$131.52	6.415%	$139.957	$139.96	$139.95	$140.00
Purchase #7	$211.54	9.386%	$231.3951	$231.40	$231.40	$231.40
7 purchase totals =	$920.03		$1,002.5996	$1,002.60	$1,002.60	$1,002.70