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	$11.53	9.513%	$12.6268	$12.63	$12.65	$12.60
Purchase #2	$184.25	3.748%	$191.1557	$191.16	$191.15	$191.20
Purchase #3	$72.79	10.286%	$80.2772	$80.28	$80.30	$80.30
Purchase #4	$99.30	9.639%	$108.8715	$108.87	$108.85	$108.90
Purchase #5	$78.74	12.238%	$88.3762	$88.38	$88.40	$88.40
Purchase #6	$168.41	11.153%	$187.1928	$187.19	$187.20	$187.20
Purchase #7	$100.83	3.157%	$104.0132	$104.01	$104.00	$104.00
7 purchase totals =	$715.85		$772.5134	$772.52	$772.55	$772.60