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	$159.96	8.375%	$173.3567	$173.36	$173.35	$173.40
Purchase #2	$187.38	5.203%	$197.1294	$197.13	$197.15	$197.10
Purchase #3	$52.81	13.466%	$59.9214	$59.92	$59.90	$59.90
Purchase #4	$44.84	13.451%	$50.8714	$50.87	$50.85	$50.90
Purchase #5	$158.81	8.339%	$172.0532	$172.05	$172.05	$172.10
Purchase #6	$230.48	5.530%	$243.2255	$243.23	$243.25	$243.20
Purchase #7	$76.40	7.645%	$82.2408	$82.24	$82.25	$82.20
7 purchase totals =	$910.68		$978.7984	$978.80	$978.80	$978.80