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	$17.58	10.762%	$19.472	$19.47	$19.45	$19.50
Purchase #2	$234.65	12.507%	$263.9977	$264.00	$264.00	$264.00
Purchase #3	$37.27	12.234%	$41.8296	$41.83	$41.85	$41.80
Purchase #4	$222.43	6.579%	$237.0637	$237.06	$237.05	$237.10
Purchase #5	$90.75	12.249%	$101.866	$101.87	$101.85	$101.90
Purchase #6	$20.78	6.524%	$22.1357	$22.14	$22.15	$22.10
Purchase #7	$38.89	11.538%	$43.3771	$43.38	$43.40	$43.40
7 purchase totals =	$662.35		$729.7418	$729.75	$729.75	$729.80