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	$168.46	11.482%	$187.8026	$187.80	$187.80	$187.80
Purchase #2	$50.40	10.291%	$55.5867	$55.59	$55.60	$55.60
Purchase #3	$69.32	4.116%	$72.1732	$72.17	$72.15	$72.20
Purchase #4	$243.75	13.603%	$276.9073	$276.91	$276.90	$276.90
Purchase #5	$151.77	5.820%	$160.603	$160.60	$160.60	$160.60
Purchase #6	$131.28	11.315%	$146.1343	$146.13	$146.15	$146.10
Purchase #7	$10.29	6.863%	$10.9962	$11.00	$11.00	$11.00
7 purchase totals =	$825.27		$910.2033	$910.20	$910.20	$910.20