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	$153.88	13.422%	$174.5338	$174.53	$174.55	$174.50
Purchase #2	$65.86	10.273%	$72.6258	$72.63	$72.65	$72.60
Purchase #3	$53.34	9.833%	$58.5849	$58.58	$58.60	$58.60
Purchase #4	$37.40	8.318%	$40.5109	$40.51	$40.50	$40.50
Purchase #5	$160.79	8.187%	$173.9539	$173.95	$173.95	$174.00
Purchase #6	$38.28	5.300%	$40.3088	$40.31	$40.30	$40.30
Purchase #7	$14.74	4.363%	$15.3831	$15.38	$15.40	$15.40
7 purchase totals =	$524.29		$575.9012	$575.89	$575.95	$575.90