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	$43.26	11.567%	$48.2639	$48.26	$48.25	$48.30
Purchase #2	$204.66	5.610%	$216.1414	$216.14	$216.15	$216.10
Purchase #3	$42.80	7.294%	$45.9218	$45.92	$45.90	$45.90
Purchase #4	$160.28	13.282%	$181.5684	$181.57	$181.55	$181.60
Purchase #5	$229.25	13.430%	$260.0383	$260.04	$260.05	$260.00
Purchase #6	$178.98	7.514%	$192.4286	$192.43	$192.45	$192.40
Purchase #7	$236.71	6.436%	$251.9447	$251.94	$251.95	$251.90
7 purchase totals =	$1,095.94		$1,196.3071	$1,196.30	$1,196.30	$1,196.20