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	$88.41	6.629%	$94.2707	$94.27	$94.25	$94.30
Purchase #2	$242.47	10.322%	$267.4978	$267.50	$267.50	$267.50
Purchase #3	$143.88	6.426%	$153.1257	$153.13	$153.15	$153.10
Purchase #4	$138.83	11.680%	$155.0453	$155.05	$155.05	$155.00
Purchase #5	$99.44	12.444%	$111.8143	$111.81	$111.80	$111.80
Purchase #6	$170.87	9.832%	$187.6699	$187.67	$187.65	$187.70
Purchase #7	$103.93	11.600%	$115.9859	$115.99	$116.00	$116.00
7 purchase totals =	$987.83		$1,085.4096	$1,085.42	$1,085.40	$1,085.40