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	$172.32	3.382%	$178.1479	$178.15	$178.15	$178.10
Purchase #2	$14.33	10.787%	$15.8758	$15.88	$15.90	$15.90
Purchase #3	$97.87	13.820%	$111.3956	$111.40	$111.40	$111.40
Purchase #4	$159.49	13.756%	$181.4294	$181.43	$181.45	$181.40
Purchase #5	$52.85	5.763%	$55.8957	$55.90	$55.90	$55.90
Purchase #6	$55.74	12.103%	$62.4862	$62.49	$62.50	$62.50
Purchase #7	$196.81	11.716%	$219.8683	$219.87	$219.85	$219.90
7 purchase totals =	$749.41		$825.0989	$825.12	$825.15	$825.10