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	$90.89	7.800%	$97.9794	$97.98	$98.00	$98.00
Purchase #2	$212.78	6.337%	$226.2639	$226.26	$226.25	$226.30
Purchase #3	$111.76	13.768%	$127.1471	$127.15	$127.15	$127.10
Purchase #4	$233.31	9.541%	$255.5701	$255.57	$255.55	$255.60
Purchase #5	$137.55	11.806%	$153.7892	$153.79	$153.80	$153.80
Purchase #6	$134.55	10.863%	$149.1662	$149.17	$149.15	$149.20
Purchase #7	$37.39	3.335%	$38.637	$38.64	$38.65	$38.60
7 purchase totals =	$958.23		$1,048.5529	$1,048.56	$1,048.55	$1,048.60