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	$114.95	10.852%	$127.4244	$127.42	$127.40	$127.40
Purchase #2	$119.59	7.614%	$128.6956	$128.70	$128.70	$128.70
Purchase #3	$244.45	7.324%	$262.3535	$262.35	$262.35	$262.40
Purchase #4	$128.77	7.108%	$137.923	$137.92	$137.90	$137.90
Purchase #5	$86.87	6.434%	$92.4592	$92.46	$92.45	$92.50
Purchase #6	$133.85	11.771%	$149.6055	$149.61	$149.60	$149.60
Purchase #7	$249.35	10.222%	$274.8386	$274.84	$274.85	$274.80
7 purchase totals =	$1,077.83		$1,173.2998	$1,173.30	$1,173.25	$1,173.30