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	$173.72	13.301%	$196.8265	$196.83	$196.85	$196.80
Purchase #2	$13.92	9.830%	$15.2883	$15.29	$15.30	$15.30
Purchase #3	$112.38	5.681%	$118.7643	$118.76	$118.75	$118.80
Purchase #4	$82.87	6.397%	$88.1712	$88.17	$88.15	$88.20
Purchase #5	$108.99	10.738%	$120.6933	$120.69	$120.70	$120.70
Purchase #6	$20.27	5.580%	$21.4011	$21.40	$21.40	$21.40
Purchase #7	$6.87	3.533%	$7.1127	$7.11	$7.10	$7.10
7 purchase totals =	$519.02		$568.2574	$568.25	$568.25	$568.30