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	$43.61	10.810%	$48.3242	$48.32	$48.30	$48.30
Purchase #2	$9.71	4.600%	$10.1567	$10.16	$10.15	$10.20
Purchase #3	$19.25	5.662%	$20.3399	$20.34	$20.35	$20.30
Purchase #4	$176.90	8.737%	$192.3558	$192.36	$192.35	$192.40
Purchase #5	$120.55	13.262%	$136.5373	$136.54	$136.55	$136.50
Purchase #6	$82.33	10.235%	$90.7565	$90.76	$90.75	$90.80
Purchase #7	$44.26	4.864%	$46.4128	$46.41	$46.40	$46.40
7 purchase totals =	$496.61		$544.8832	$544.89	$544.85	$544.90