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	$190.28	4.644%	$199.1166	$199.12	$199.10	$199.10
Purchase #2	$120.50	11.672%	$134.5648	$134.56	$134.55	$134.60
Purchase #3	$101.40	10.447%	$111.9933	$111.99	$112.00	$112.00
Purchase #4	$43.82	11.612%	$48.9084	$48.91	$48.90	$48.90
Purchase #5	$172.80	3.562%	$178.9551	$178.96	$178.95	$179.00
Purchase #6	$214.69	12.390%	$241.2901	$241.29	$241.30	$241.30
Purchase #7	$169.92	9.539%	$186.1287	$186.13	$186.15	$186.10
7 purchase totals =	$1,013.41		$1,100.9570	$1,100.96	$1,100.95	$1,101.00