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	$75.28	13.260%	$85.2621	$85.26	$85.25	$85.30
Purchase #2	$137.91	3.805%	$143.1575	$143.16	$143.15	$143.20
Purchase #3	$126.46	4.151%	$131.7094	$131.71	$131.70	$131.70
Purchase #4	$100.78	11.628%	$112.4987	$112.50	$112.50	$112.50
Purchase #5	$243.39	9.841%	$267.342	$267.34	$267.35	$267.30
Purchase #6	$133.37	3.339%	$137.8232	$137.82	$137.80	$137.80
Purchase #7	$145.43	11.481%	$162.1268	$162.13	$162.15	$162.10
7 purchase totals =	$962.62		$1,039.9197	$1,039.92	$1,039.90	$1,039.90