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	$200.49	7.717%	$215.9618	$215.96	$215.95	$216.00
Purchase #2	$192.39	6.343%	$204.5933	$204.59	$204.60	$204.60
Purchase #3	$138.27	5.178%	$145.4296	$145.43	$145.45	$145.40
Purchase #4	$49.65	4.592%	$51.9299	$51.93	$51.95	$51.90
Purchase #5	$79.33	12.424%	$89.186	$89.19	$89.20	$89.20
Purchase #6	$229.99	9.505%	$251.8505	$251.85	$251.85	$251.90
Purchase #7	$76.38	13.787%	$86.9105	$86.91	$86.90	$86.90
7 purchase totals =	$966.50		$1,045.8616	$1,045.86	$1,045.90	$1,045.90