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	$90.59	12.144%	$101.5912	$101.59	$101.60	$101.60
Purchase #2	$161.35	10.325%	$178.0094	$178.01	$178.00	$178.00
Purchase #3	$248.63	7.562%	$267.4314	$267.43	$267.45	$267.40
Purchase #4	$55.64	8.501%	$60.37	$60.37	$60.35	$60.40
Purchase #5	$160.28	8.202%	$173.4262	$173.43	$173.45	$173.40
Purchase #6	$180.89	6.104%	$191.9315	$191.93	$191.95	$191.90
Purchase #7	$97.40	8.359%	$105.5417	$105.54	$105.55	$105.50
7 purchase totals =	$994.78		$1,078.3014	$1,078.30	$1,078.35	$1,078.20