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	$167.84	13.727%	$190.8794	$190.88	$190.90	$190.90
Purchase #2	$48.92	5.742%	$51.729	$51.73	$51.75	$51.70
Purchase #3	$64.85	3.308%	$66.9952	$67.00	$67.00	$67.00
Purchase #4	$178.64	5.217%	$187.9596	$187.96	$187.95	$188.00
Purchase #5	$154.28	11.176%	$171.5223	$171.52	$171.50	$171.50
Purchase #6	$235.84	6.636%	$251.4903	$251.49	$251.50	$251.50
Purchase #7	$181.25	5.286%	$190.8309	$190.83	$190.85	$190.80
7 purchase totals =	$1,031.62		$1,111.4067	$1,111.41	$1,111.45	$1,111.40