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	$154.43	11.730%	$172.5446	$172.54	$172.55	$172.50
Purchase #2	$153.30	13.603%	$174.1534	$174.15	$174.15	$174.20
Purchase #3	$171.51	9.701%	$188.1482	$188.15	$188.15	$188.10
Purchase #4	$97.86	3.811%	$101.5894	$101.59	$101.60	$101.60
Purchase #5	$39.67	6.647%	$42.3069	$42.31	$42.30	$42.30
Purchase #6	$82.84	4.141%	$86.2704	$86.27	$86.25	$86.30
Purchase #7	$8.68	5.251%	$9.1358	$9.14	$9.15	$9.10
7 purchase totals =	$708.29		$774.1487	$774.15	$774.15	$774.10