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	$185.52	7.221%	$198.9164	$198.92	$198.90	$198.90
Purchase #2	$165.59	9.697%	$181.6473	$181.65	$181.65	$181.60
Purchase #3	$10.89	11.140%	$12.1031	$12.10	$12.10	$12.10
Purchase #4	$203.38	12.223%	$228.2391	$228.24	$228.25	$228.20
Purchase #5	$143.88	3.222%	$148.5158	$148.52	$148.50	$148.50
Purchase #6	$175.60	7.867%	$189.4145	$189.41	$189.40	$189.40
Purchase #7	$78.42	9.348%	$85.7507	$85.75	$85.75	$85.80
7 purchase totals =	$963.28		$1,044.5869	$1,044.59	$1,044.55	$1,044.50