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	$99.66	13.288%	$112.9028	$112.90	$112.90	$112.90
Purchase #2	$185.75	11.222%	$206.5949	$206.59	$206.60	$206.60
Purchase #3	$140.28	3.674%	$145.4339	$145.43	$145.45	$145.40
Purchase #4	$214.52	4.370%	$223.8945	$223.89	$223.90	$223.90
Purchase #5	$168.50	9.128%	$183.8807	$183.88	$183.90	$183.90
Purchase #6	$186.86	4.293%	$194.8819	$194.88	$194.90	$194.90
Purchase #7	$201.70	7.521%	$216.8699	$216.87	$216.85	$216.90
7 purchase totals =	$1,197.27		$1,284.4586	$1,284.44	$1,284.50	$1,284.50