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	$15.69	9.196%	$17.1329	$17.13	$17.15	$17.10
Purchase #2	$18.50	11.359%	$20.6014	$20.60	$20.60	$20.60
Purchase #3	$58.30	5.125%	$61.2879	$61.29	$61.30	$61.30
Purchase #4	$238.70	10.374%	$263.4627	$263.46	$263.45	$263.50
Purchase #5	$82.84	9.625%	$90.8134	$90.81	$90.80	$90.80
Purchase #6	$150.94	3.612%	$156.392	$156.39	$156.40	$156.40
Purchase #7	$111.36	6.343%	$118.4236	$118.42	$118.40	$118.40
7 purchase totals =	$676.33		$728.1139	$728.10	$728.10	$728.10