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	$65.96	9.352%	$72.1286	$72.13	$72.15	$72.10
Purchase #2	$91.96	5.344%	$96.8743	$96.87	$96.85	$96.90
Purchase #3	$23.49	12.278%	$26.3741	$26.37	$26.35	$26.40
Purchase #4	$94.43	6.382%	$100.4565	$100.46	$100.45	$100.50
Purchase #5	$80.78	12.610%	$90.9664	$90.97	$90.95	$91.00
Purchase #6	$244.82	8.745%	$266.2295	$266.23	$266.25	$266.20
Purchase #7	$140.42	4.542%	$146.7979	$146.80	$146.80	$146.80
7 purchase totals =	$741.86		$799.8273	$799.83	$799.80	$799.90