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	$86.52	10.747%	$95.8183	$95.82	$95.80	$95.80
Purchase #2	$154.35	5.353%	$162.6124	$162.61	$162.60	$162.60
Purchase #3	$219.50	3.188%	$226.4977	$226.50	$226.50	$226.50
Purchase #4	$36.46	13.627%	$41.4284	$41.43	$41.45	$41.40
Purchase #5	$218.52	13.657%	$248.3633	$248.36	$248.35	$248.40
Purchase #6	$84.27	6.161%	$89.4619	$89.46	$89.45	$89.50
Purchase #7	$98.62	5.375%	$103.9208	$103.92	$103.90	$103.90
7 purchase totals =	$898.24		$968.1028	$968.10	$968.05	$968.10