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	$241.96	7.590%	$260.3248	$260.32	$260.30	$260.30
Purchase #2	$16.82	10.678%	$18.616	$18.62	$18.60	$18.60
Purchase #3	$127.40	13.174%	$144.1837	$144.18	$144.20	$144.20
Purchase #4	$90.37	6.808%	$96.5224	$96.52	$96.50	$96.50
Purchase #5	$127.44	12.621%	$143.5242	$143.52	$143.50	$143.50
Purchase #6	$103.47	12.317%	$116.2144	$116.21	$116.20	$116.20
Purchase #7	$199.68	11.146%	$221.9363	$221.94	$221.95	$221.90
7 purchase totals =	$907.14		$1,001.3218	$1,001.31	$1,001.25	$1,001.20