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	$127.36	4.784%	$133.4529	$133.45	$133.45	$133.50
Purchase #2	$79.84	8.760%	$86.834	$86.83	$86.85	$86.80
Purchase #3	$139.29	4.158%	$145.0817	$145.08	$145.10	$145.10
Purchase #4	$53.60	13.818%	$61.0064	$61.01	$61.00	$61.00
Purchase #5	$199.71	12.727%	$225.1271	$225.13	$225.15	$225.10
Purchase #6	$33.86	5.243%	$35.6353	$35.64	$35.65	$35.60
Purchase #7	$78.64	10.487%	$86.887	$86.89	$86.90	$86.90
7 purchase totals =	$712.30		$774.0244	$774.03	$774.10	$774.00