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	$201.69	11.322%	$224.5253	$224.53	$224.55	$224.50
Purchase #2	$72.64	4.746%	$76.0875	$76.09	$76.10	$76.10
Purchase #3	$68.41	4.247%	$71.3154	$71.32	$71.30	$71.30
Purchase #4	$226.90	5.810%	$240.0829	$240.08	$240.10	$240.10
Purchase #5	$55.36	7.631%	$59.5845	$59.58	$59.60	$59.60
Purchase #6	$194.35	10.465%	$214.6887	$214.69	$214.70	$214.70
Purchase #7	$95.90	13.118%	$108.4802	$108.48	$108.50	$108.50
7 purchase totals =	$915.25		$994.7645	$994.77	$994.85	$994.80