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	$207.71	8.117%	$224.5698	$224.57	$224.55	$224.60
Purchase #2	$210.57	4.153%	$219.315	$219.32	$219.30	$219.30
Purchase #3	$243.82	11.255%	$271.2619	$271.26	$271.25	$271.30
Purchase #4	$21.83	3.531%	$22.6008	$22.60	$22.60	$22.60
Purchase #5	$93.56	7.589%	$100.6603	$100.66	$100.65	$100.70
Purchase #6	$151.86	10.510%	$167.8205	$167.82	$167.80	$167.80
Purchase #7	$32.48	8.298%	$35.1752	$35.18	$35.20	$35.20
7 purchase totals =	$961.83		$1,041.4035	$1,041.41	$1,041.35	$1,041.50