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	$173.80	6.650%	$185.3577	$185.36	$185.35	$185.40
Purchase #2	$91.62	4.526%	$95.7667	$95.77	$95.75	$95.80
Purchase #3	$19.44	3.201%	$20.0623	$20.06	$20.05	$20.10
Purchase #4	$10.73	9.730%	$11.774	$11.77	$11.75	$11.80
Purchase #5	$105.43	11.757%	$117.8254	$117.83	$117.85	$117.80
Purchase #6	$118.32	4.706%	$123.8881	$123.89	$123.90	$123.90
Purchase #7	$231.92	8.333%	$251.2459	$251.25	$251.25	$251.20
7 purchase totals =	$751.26		$805.9201	$805.93	$805.90	$806.00