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	$163.94	5.137%	$172.3616	$172.36	$172.35	$172.40
Purchase #2	$9.91	6.166%	$10.5211	$10.52	$10.50	$10.50
Purchase #3	$37.80	12.233%	$42.4241	$42.42	$42.40	$42.40
Purchase #4	$208.26	8.110%	$225.1499	$225.15	$225.15	$225.10
Purchase #5	$19.89	8.570%	$21.5946	$21.59	$21.60	$21.60
Purchase #6	$70.55	4.534%	$73.7487	$73.75	$73.75	$73.70
Purchase #7	$237.98	5.796%	$251.7733	$251.77	$251.75	$251.80
7 purchase totals =	$748.33		$797.5733	$797.56	$797.50	$797.50