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	$184.44	6.595%	$196.6038	$196.60	$196.60	$196.60
Purchase #2	$113.43	13.130%	$128.3234	$128.32	$128.30	$128.30
Purchase #3	$39.75	3.577%	$41.1719	$41.17	$41.15	$41.20
Purchase #4	$177.63	10.490%	$196.2634	$196.26	$196.25	$196.30
Purchase #5	$29.81	10.765%	$33.019	$33.02	$33.00	$33.00
Purchase #6	$107.45	3.413%	$111.1173	$111.12	$111.10	$111.10
Purchase #7	$156.88	10.754%	$173.7509	$173.75	$173.75	$173.80
7 purchase totals =	$809.39		$880.2497	$880.24	$880.15	$880.30