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	$153.67	10.753%	$170.1941	$170.19	$170.20	$170.20
Purchase #2	$175.36	10.510%	$193.7903	$193.79	$193.80	$193.80
Purchase #3	$211.70	4.518%	$221.2646	$221.26	$221.25	$221.30
Purchase #4	$98.86	13.858%	$112.56	$112.56	$112.55	$112.60
Purchase #5	$230.87	5.283%	$243.0669	$243.07	$243.05	$243.10
Purchase #6	$108.46	3.822%	$112.6053	$112.61	$112.60	$112.60
Purchase #7	$127.68	11.863%	$142.8267	$142.83	$142.85	$142.80
7 purchase totals =	$1,106.60		$1,196.3079	$1,196.31	$1,196.30	$1,196.40