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	$79.66	7.728%	$85.8161	$85.82	$85.80	$85.80
Purchase #2	$93.91	3.210%	$96.9245	$96.92	$96.90	$96.90
Purchase #3	$204.95	13.852%	$233.3397	$233.34	$233.35	$233.30
Purchase #4	$66.48	12.113%	$74.5327	$74.53	$74.55	$74.50
Purchase #5	$123.45	6.530%	$131.5113	$131.51	$131.50	$131.50
Purchase #6	$149.78	13.854%	$170.5305	$170.53	$170.55	$170.50
Purchase #7	$187.82	8.874%	$204.4871	$204.49	$204.50	$204.50
7 purchase totals =	$906.05		$997.1419	$997.14	$997.15	$997.00