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	$107.50	4.765%	$112.6224	$112.62	$112.60	$112.60
Purchase #2	$246.50	3.614%	$255.4085	$255.41	$255.40	$255.40
Purchase #3	$54.89	10.414%	$60.6062	$60.61	$60.60	$60.60
Purchase #4	$142.62	12.126%	$159.9141	$159.91	$159.90	$159.90
Purchase #5	$179.38	8.365%	$194.3851	$194.39	$194.40	$194.40
Purchase #6	$145.40	8.479%	$157.7285	$157.73	$157.75	$157.70
Purchase #7	$143.64	4.873%	$150.6396	$150.64	$150.65	$150.60
7 purchase totals =	$1,019.93		$1,091.3044	$1,091.31	$1,091.30	$1,091.20