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	$181.91	13.188%	$205.9003	$205.90	$205.90	$205.90
Purchase #2	$52.74	6.628%	$56.2356	$56.24	$56.25	$56.20
Purchase #3	$180.85	13.620%	$205.4818	$205.48	$205.50	$205.50
Purchase #4	$201.49	10.581%	$222.8097	$222.81	$222.80	$222.80
Purchase #5	$147.66	3.115%	$152.2596	$152.26	$152.25	$152.30
Purchase #6	$111.89	13.381%	$126.862	$126.86	$126.85	$126.90
Purchase #7	$115.48	10.402%	$127.4922	$127.49	$127.50	$127.50
7 purchase totals =	$992.02		$1,097.0412	$1,097.04	$1,097.05	$1,097.10