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	$42.86	6.574%	$45.6776	$45.68	$45.70	$45.70
Purchase #2	$232.51	10.374%	$256.6306	$256.63	$256.65	$256.60
Purchase #3	$66.88	5.249%	$70.3905	$70.39	$70.40	$70.40
Purchase #4	$96.89	3.413%	$100.1969	$100.20	$100.20	$100.20
Purchase #5	$165.69	10.237%	$182.6517	$182.65	$182.65	$182.70
Purchase #6	$151.52	4.579%	$158.4581	$158.46	$158.45	$158.50
Purchase #7	$62.35	13.732%	$70.9119	$70.91	$70.90	$70.90
7 purchase totals =	$818.70		$884.9173	$884.92	$884.95	$885.00