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	$91.28	6.122%	$96.8682	$96.87	$96.85	$96.90
Purchase #2	$110.55	3.852%	$114.8084	$114.81	$114.80	$114.80
Purchase #3	$107.93	3.197%	$111.3805	$111.38	$111.40	$111.40
Purchase #4	$83.62	4.196%	$87.1287	$87.13	$87.15	$87.10
Purchase #5	$220.98	5.592%	$233.3372	$233.34	$233.35	$233.30
Purchase #6	$104.88	12.137%	$117.6093	$117.61	$117.60	$117.60
Purchase #7	$190.50	10.429%	$210.3672	$210.37	$210.35	$210.40
7 purchase totals =	$909.74		$971.4995	$971.51	$971.50	$971.50