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	$183.82	7.744%	$198.055	$198.06	$198.05	$198.10
Purchase #2	$5.96	10.837%	$6.6059	$6.61	$6.60	$6.60
Purchase #3	$102.45	8.647%	$111.3089	$111.31	$111.30	$111.30
Purchase #4	$110.52	6.235%	$117.4109	$117.41	$117.40	$117.40
Purchase #5	$173.51	11.126%	$192.8147	$192.81	$192.80	$192.80
Purchase #6	$26.29	13.821%	$29.9235	$29.92	$29.90	$29.90
Purchase #7	$116.76	9.784%	$128.1838	$128.18	$128.20	$128.20
7 purchase totals =	$719.31		$784.3027	$784.30	$784.25	$784.30