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	$48.89	6.569%	$52.1016	$52.10	$52.10	$52.10
Purchase #2	$178.54	11.607%	$199.2631	$199.26	$199.25	$199.30
Purchase #3	$188.49	6.568%	$200.87	$200.87	$200.85	$200.90
Purchase #4	$224.73	6.722%	$239.8364	$239.84	$239.85	$239.80
Purchase #5	$66.33	6.443%	$70.6036	$70.60	$70.60	$70.60
Purchase #6	$44.32	13.699%	$50.3914	$50.39	$50.40	$50.40
Purchase #7	$140.64	3.384%	$145.3993	$145.40	$145.40	$145.40
7 purchase totals =	$891.94		$958.4654	$958.46	$958.45	$958.50