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	$59.27	3.297%	$61.2241	$61.22	$61.20	$61.20
Purchase #2	$220.42	3.118%	$227.2927	$227.29	$227.30	$227.30
Purchase #3	$55.66	9.641%	$61.0262	$61.03	$61.05	$61.00
Purchase #4	$42.36	10.471%	$46.7955	$46.80	$46.80	$46.80
Purchase #5	$240.69	7.123%	$257.8343	$257.83	$257.85	$257.80
Purchase #6	$162.65	6.780%	$173.6777	$173.68	$173.70	$173.70
Purchase #7	$176.66	7.591%	$190.0703	$190.07	$190.05	$190.10
7 purchase totals =	$957.71		$1,017.9208	$1,017.92	$1,017.95	$1,017.90