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	$183.50	13.289%	$207.8853	$207.89	$207.90	$207.90
Purchase #2	$59.79	12.189%	$67.0778	$67.08	$67.10	$67.10
Purchase #3	$62.70	4.530%	$65.5403	$65.54	$65.55	$65.50
Purchase #4	$79.72	8.849%	$86.7744	$86.77	$86.75	$86.80
Purchase #5	$93.34	10.504%	$103.1444	$103.14	$103.15	$103.10
Purchase #6	$176.84	11.248%	$196.731	$196.73	$196.75	$196.70
Purchase #7	$73.71	6.365%	$78.4016	$78.40	$78.40	$78.40
7 purchase totals =	$729.60		$805.5548	$805.55	$805.60	$805.50