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	$14.82	6.687%	$15.811	$15.81	$15.80	$15.80
Purchase #2	$76.56	12.139%	$85.8536	$85.85	$85.85	$85.90
Purchase #3	$95.65	8.613%	$103.8883	$103.89	$103.90	$103.90
Purchase #4	$38.90	13.749%	$44.2484	$44.25	$44.25	$44.20
Purchase #5	$233.25	7.249%	$250.1583	$250.16	$250.15	$250.20
Purchase #6	$74.30	11.874%	$83.1224	$83.12	$83.10	$83.10
Purchase #7	$105.73	9.851%	$116.1455	$116.15	$116.15	$116.10
7 purchase totals =	$639.21		$699.2275	$699.23	$699.20	$699.20