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	$153.86	12.284%	$172.7602	$172.76	$172.75	$172.80
Purchase #2	$66.84	5.287%	$70.3738	$70.37	$70.35	$70.40
Purchase #3	$42.56	13.634%	$48.3626	$48.36	$48.35	$48.40
Purchase #4	$189.93	10.822%	$210.4842	$210.48	$210.50	$210.50
Purchase #5	$95.40	13.533%	$108.3105	$108.31	$108.30	$108.30
Purchase #6	$70.39	12.850%	$79.4351	$79.44	$79.45	$79.40
Purchase #7	$36.78	7.384%	$39.4958	$39.50	$39.50	$39.50
7 purchase totals =	$655.76		$729.2222	$729.22	$729.20	$729.30