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	$60.77	6.348%	$64.6277	$64.63	$64.65	$64.60
Purchase #2	$140.25	8.680%	$152.4237	$152.42	$152.40	$152.40
Purchase #3	$219.55	10.562%	$242.7389	$242.74	$242.75	$242.70
Purchase #4	$12.28	13.121%	$13.8913	$13.89	$13.90	$13.90
Purchase #5	$189.31	4.635%	$198.0845	$198.08	$198.10	$198.10
Purchase #6	$183.35	9.336%	$200.4676	$200.47	$200.45	$200.50
Purchase #7	$94.60	6.117%	$100.3867	$100.39	$100.40	$100.40
7 purchase totals =	$900.11		$972.6204	$972.62	$972.65	$972.60