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	$16.32	7.488%	$17.542	$17.54	$17.55	$17.50
Purchase #2	$42.58	6.659%	$45.4154	$45.42	$45.40	$45.40
Purchase #3	$74.52	3.717%	$77.2899	$77.29	$77.30	$77.30
Purchase #4	$75.43	13.311%	$85.4705	$85.47	$85.45	$85.50
Purchase #5	$182.82	9.538%	$200.2574	$200.26	$200.25	$200.30
Purchase #6	$71.61	13.777%	$81.4757	$81.48	$81.50	$81.50
Purchase #7	$230.60	8.674%	$250.6022	$250.60	$250.60	$250.60
7 purchase totals =	$693.88		$758.0531	$758.06	$758.05	$758.10