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	$56.38	12.669%	$63.5228	$63.52	$63.50	$63.50
Purchase #2	$14.66	4.676%	$15.3455	$15.35	$15.35	$15.30
Purchase #3	$64.84	4.678%	$67.8732	$67.87	$67.85	$67.90
Purchase #4	$123.26	3.563%	$127.6518	$127.65	$127.65	$127.70
Purchase #5	$138.78	12.829%	$156.5841	$156.58	$156.60	$156.60
Purchase #6	$41.78	12.139%	$46.8517	$46.85	$46.85	$46.90
Purchase #7	$110.39	10.143%	$121.5869	$121.59	$121.60	$121.60
7 purchase totals =	$550.09		$599.4160	$599.41	$599.40	$599.50