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	$130.40	10.838%	$144.5328	$144.53	$144.55	$144.50
Purchase #2	$86.78	11.630%	$96.8725	$96.87	$96.85	$96.90
Purchase #3	$12.35	7.475%	$13.2732	$13.27	$13.25	$13.30
Purchase #4	$217.53	11.530%	$242.6112	$242.61	$242.60	$242.60
Purchase #5	$41.42	10.474%	$45.7583	$45.76	$45.75	$45.80
Purchase #6	$64.48	8.321%	$69.8454	$69.85	$69.85	$69.80
Purchase #7	$169.29	8.505%	$183.6881	$183.69	$183.70	$183.70
7 purchase totals =	$722.25		$796.5815	$796.58	$796.55	$796.60