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	$232.31	10.528%	$256.7676	$256.77	$256.75	$256.80
Purchase #2	$31.56	9.291%	$34.4922	$34.49	$34.50	$34.50
Purchase #3	$54.51	9.277%	$59.5669	$59.57	$59.55	$59.60
Purchase #4	$65.91	13.511%	$74.8151	$74.82	$74.80	$74.80
Purchase #5	$242.95	13.551%	$275.8722	$275.87	$275.85	$275.90
Purchase #6	$230.90	6.513%	$245.9385	$245.94	$245.95	$245.90
Purchase #7	$206.88	10.130%	$227.8369	$227.84	$227.85	$227.80
7 purchase totals =	$1,065.02		$1,175.2894	$1,175.30	$1,175.25	$1,175.30