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	$181.85	6.873%	$194.3486	$194.35	$194.35	$194.30
Purchase #2	$89.31	11.569%	$99.6423	$99.64	$99.65	$99.60
Purchase #3	$70.75	11.247%	$78.7073	$78.71	$78.70	$78.70
Purchase #4	$154.79	13.490%	$175.6712	$175.67	$175.65	$175.70
Purchase #5	$13.69	5.584%	$14.4544	$14.45	$14.45	$14.50
Purchase #6	$68.31	10.137%	$75.2346	$75.23	$75.25	$75.20
Purchase #7	$132.60	9.700%	$145.4622	$145.46	$145.45	$145.50
7 purchase totals =	$711.30		$783.5206	$783.51	$783.50	$783.50