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	$221.43	9.413%	$242.2732	$242.27	$242.25	$242.30
Purchase #2	$190.28	9.751%	$208.8342	$208.83	$208.85	$208.80
Purchase #3	$147.35	7.341%	$158.167	$158.17	$158.15	$158.20
Purchase #4	$163.92	6.516%	$174.601	$174.60	$174.60	$174.60
Purchase #5	$90.62	4.388%	$94.5964	$94.60	$94.60	$94.60
Purchase #6	$25.72	8.509%	$27.9085	$27.91	$27.90	$27.90
Purchase #7	$169.88	10.714%	$188.0809	$188.08	$188.10	$188.10
7 purchase totals =	$1,009.20		$1,094.4612	$1,094.46	$1,094.45	$1,094.50