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	$143.71	10.584%	$158.9203	$158.92	$158.90	$158.90
Purchase #2	$80.53	13.692%	$91.5562	$91.56	$91.55	$91.60
Purchase #3	$120.95	5.193%	$127.2309	$127.23	$127.25	$127.20
Purchase #4	$216.75	5.325%	$228.2919	$228.29	$228.30	$228.30
Purchase #5	$175.92	3.831%	$182.6595	$182.66	$182.65	$182.70
Purchase #6	$32.73	4.662%	$34.2559	$34.26	$34.25	$34.30
Purchase #7	$143.31	10.665%	$158.594	$158.59	$158.60	$158.60
7 purchase totals =	$913.90		$981.5087	$981.51	$981.50	$981.60