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	$83.62	11.405%	$93.1569	$93.16	$93.15	$93.20
Purchase #2	$213.59	13.446%	$242.3093	$242.31	$242.30	$242.30
Purchase #3	$205.52	12.330%	$230.8606	$230.86	$230.85	$230.90
Purchase #4	$207.89	8.426%	$225.4068	$225.41	$225.40	$225.40
Purchase #5	$228.54	11.864%	$255.654	$255.65	$255.65	$255.70
Purchase #6	$114.29	11.729%	$127.6951	$127.70	$127.70	$127.70
Purchase #7	$212.79	11.185%	$236.5906	$236.59	$236.60	$236.60
7 purchase totals =	$1,266.24		$1,411.6733	$1,411.68	$1,411.65	$1,411.80