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	$158.94	4.390%	$165.9175	$165.92	$165.90	$165.90
Purchase #2	$117.65	10.227%	$129.6821	$129.68	$129.70	$129.70
Purchase #3	$135.50	12.140%	$151.9497	$151.95	$151.95	$151.90
Purchase #4	$183.79	8.558%	$199.5187	$199.52	$199.50	$199.50
Purchase #5	$151.29	3.193%	$156.1207	$156.12	$156.10	$156.10
Purchase #6	$151.73	12.382%	$170.5172	$170.52	$170.50	$170.50
Purchase #7	$89.52	12.188%	$100.4307	$100.43	$100.45	$100.40
7 purchase totals =	$988.42		$1,074.1366	$1,074.14	$1,074.10	$1,074.00