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	$162.33	13.830%	$184.7802	$184.78	$184.80	$184.80
Purchase #2	$215.25	5.743%	$227.6118	$227.61	$227.60	$227.60
Purchase #3	$157.85	9.367%	$172.6358	$172.64	$172.65	$172.60
Purchase #4	$143.75	5.762%	$152.0329	$152.03	$152.05	$152.00
Purchase #5	$168.39	3.460%	$174.2163	$174.22	$174.20	$174.20
Purchase #6	$116.78	13.370%	$132.3935	$132.39	$132.40	$132.40
Purchase #7	$72.79	11.467%	$81.1368	$81.14	$81.15	$81.10
7 purchase totals =	$1,037.14		$1,124.8073	$1,124.81	$1,124.85	$1,124.70