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	$76.30	8.711%	$82.9465	$82.95	$82.95	$82.90
Purchase #2	$47.25	10.254%	$52.095	$52.10	$52.10	$52.10
Purchase #3	$147.69	11.247%	$164.3007	$164.30	$164.30	$164.30
Purchase #4	$145.68	3.827%	$151.2552	$151.26	$151.25	$151.30
Purchase #5	$211.94	7.639%	$228.1301	$228.13	$228.15	$228.10
Purchase #6	$81.58	13.435%	$92.5403	$92.54	$92.55	$92.50
Purchase #7	$111.27	5.288%	$117.154	$117.15	$117.15	$117.20
7 purchase totals =	$821.71		$888.4218	$888.43	$888.45	$888.40