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	$128.65	8.377%	$139.427	$139.43	$139.45	$139.40
Purchase #2	$114.93	10.620%	$127.1356	$127.14	$127.15	$127.10
Purchase #3	$76.68	3.533%	$79.3891	$79.39	$79.40	$79.40
Purchase #4	$48.90	7.595%	$52.614	$52.61	$52.60	$52.60
Purchase #5	$86.44	5.809%	$91.4613	$91.46	$91.45	$91.50
Purchase #6	$68.78	7.344%	$73.8312	$73.83	$73.85	$73.80
Purchase #7	$161.90	7.203%	$173.5617	$173.56	$173.55	$173.60
7 purchase totals =	$686.28		$737.4199	$737.42	$737.45	$737.40