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	$149.32	12.475%	$167.9477	$167.95	$167.95	$167.90
Purchase #2	$233.52	10.603%	$258.2801	$258.28	$258.30	$258.30
Purchase #3	$144.95	4.656%	$151.6989	$151.70	$151.70	$151.70
Purchase #4	$244.63	3.634%	$253.5199	$253.52	$253.50	$253.50
Purchase #5	$199.47	10.586%	$220.5859	$220.59	$220.60	$220.60
Purchase #6	$92.96	13.104%	$105.1415	$105.14	$105.15	$105.10
Purchase #7	$96.70	13.509%	$109.7632	$109.76	$109.75	$109.80
7 purchase totals =	$1,161.55		$1,266.9372	$1,266.94	$1,266.95	$1,266.90