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	$172.77	13.622%	$196.3047	$196.30	$196.30	$196.30
Purchase #2	$9.76	7.619%	$10.5036	$10.50	$10.50	$10.50
Purchase #3	$89.81	6.846%	$95.9584	$95.96	$95.95	$96.00
Purchase #4	$179.51	12.562%	$202.06	$202.06	$202.05	$202.10
Purchase #5	$21.84	6.610%	$23.2836	$23.28	$23.30	$23.30
Purchase #6	$6.30	7.575%	$6.7772	$6.78	$6.80	$6.80
Purchase #7	$123.78	7.156%	$132.6377	$132.64	$132.65	$132.60
7 purchase totals =	$603.77		$667.5252	$667.52	$667.55	$667.60