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	$127.53	9.362%	$139.4694	$139.47	$139.45	$139.50
Purchase #2	$193.41	5.553%	$204.1501	$204.15	$204.15	$204.20
Purchase #3	$40.94	4.772%	$42.8937	$42.89	$42.90	$42.90
Purchase #4	$241.61	5.301%	$254.4177	$254.42	$254.40	$254.40
Purchase #5	$136.60	13.636%	$155.2268	$155.23	$155.25	$155.20
Purchase #6	$40.64	7.677%	$43.7599	$43.76	$43.75	$43.80
Purchase #7	$191.46	3.325%	$197.826	$197.83	$197.85	$197.80
7 purchase totals =	$972.19		$1,037.7436	$1,037.75	$1,037.75	$1,037.80