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	$168.82	4.728%	$176.8018	$176.80	$176.80	$176.80
Purchase #2	$134.29	13.852%	$152.8919	$152.89	$152.90	$152.90
Purchase #3	$236.45	7.145%	$253.3444	$253.34	$253.35	$253.30
Purchase #4	$77.83	9.632%	$85.3266	$85.33	$85.35	$85.30
Purchase #5	$173.91	5.444%	$183.3777	$183.38	$183.40	$183.40
Purchase #6	$206.57	5.103%	$217.1113	$217.11	$217.10	$217.10
Purchase #7	$20.52	6.241%	$21.8007	$21.80	$21.80	$21.80
7 purchase totals =	$1,018.39		$1,090.6544	$1,090.65	$1,090.70	$1,090.60