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	$54.37	9.345%	$59.4509	$59.45	$59.45	$59.50
Purchase #2	$245.54	8.108%	$265.4484	$265.45	$265.45	$265.40
Purchase #3	$33.44	13.560%	$37.9745	$37.97	$37.95	$38.00
Purchase #4	$118.95	4.714%	$124.5573	$124.56	$124.55	$124.60
Purchase #5	$49.47	13.470%	$56.1336	$56.13	$56.15	$56.10
Purchase #6	$87.83	8.760%	$95.5239	$95.52	$95.50	$95.50
Purchase #7	$43.88	9.647%	$48.1131	$48.11	$48.10	$48.10
7 purchase totals =	$633.48		$687.2017	$687.19	$687.15	$687.20