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	$141.37	8.653%	$153.6027	$153.60	$153.60	$153.60
Purchase #2	$112.36	13.499%	$127.5275	$127.53	$127.55	$127.50
Purchase #3	$153.60	7.516%	$165.1446	$165.14	$165.15	$165.10
Purchase #4	$134.56	3.654%	$139.4768	$139.48	$139.50	$139.50
Purchase #5	$248.35	11.646%	$277.2728	$277.27	$277.25	$277.30
Purchase #6	$91.79	6.353%	$97.6214	$97.62	$97.60	$97.60
Purchase #7	$10.39	3.821%	$10.787	$10.79	$10.80	$10.80
7 purchase totals =	$892.42		$971.4328	$971.43	$971.45	$971.40