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	$153.47	13.757%	$174.5829	$174.58	$174.60	$174.60
Purchase #2	$196.83	3.442%	$203.6049	$203.60	$203.60	$203.60
Purchase #3	$146.31	9.567%	$160.3075	$160.31	$160.30	$160.30
Purchase #4	$222.56	6.103%	$236.1428	$236.14	$236.15	$236.10
Purchase #5	$101.37	13.215%	$114.766	$114.77	$114.75	$114.80
Purchase #6	$148.47	4.136%	$154.6107	$154.61	$154.60	$154.60
Purchase #7	$33.62	11.807%	$37.5895	$37.59	$37.60	$37.60
7 purchase totals =	$1,002.63		$1,081.6043	$1,081.60	$1,081.60	$1,081.60