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	$201.63	6.591%	$214.9194	$214.92	$214.90	$214.90
Purchase #2	$82.59	8.393%	$89.5218	$89.52	$89.50	$89.50
Purchase #3	$239.59	6.840%	$255.978	$255.98	$256.00	$256.00
Purchase #4	$85.83	9.321%	$93.8302	$93.83	$93.85	$93.80
Purchase #5	$127.58	7.215%	$136.7849	$136.78	$136.80	$136.80
Purchase #6	$192.66	6.443%	$205.0731	$205.07	$205.05	$205.10
Purchase #7	$115.35	13.579%	$131.0134	$131.01	$131.00	$131.00
7 purchase totals =	$1,045.23		$1,127.1208	$1,127.11	$1,127.10	$1,127.10