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	$186.54	7.317%	$200.1891	$200.19	$200.20	$200.20
Purchase #2	$70.48	13.852%	$80.2429	$80.24	$80.25	$80.20
Purchase #3	$54.46	8.483%	$59.0798	$59.08	$59.10	$59.10
Purchase #4	$200.37	4.162%	$208.7094	$208.71	$208.70	$208.70
Purchase #5	$72.69	5.102%	$76.3986	$76.40	$76.40	$76.40
Purchase #6	$29.89	12.399%	$33.5961	$33.60	$33.60	$33.60
Purchase #7	$51.67	5.249%	$54.3822	$54.38	$54.40	$54.40
7 purchase totals =	$666.10		$712.5981	$712.60	$712.65	$712.60