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	$60.89	5.367%	$64.158	$64.16	$64.15	$64.20
Purchase #2	$185.89	7.277%	$199.4172	$199.42	$199.40	$199.40
Purchase #3	$90.94	6.586%	$96.9293	$96.93	$96.95	$96.90
Purchase #4	$34.54	7.301%	$37.0618	$37.06	$37.05	$37.10
Purchase #5	$10.99	11.770%	$12.2835	$12.28	$12.30	$12.30
Purchase #6	$113.57	13.710%	$129.1404	$129.14	$129.15	$129.10
Purchase #7	$84.40	6.730%	$90.0801	$90.08	$90.10	$90.10
7 purchase totals =	$581.22		$629.0703	$629.07	$629.10	$629.10