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	$218.57	13.117%	$247.2398	$247.24	$247.25	$247.20
Purchase #2	$103.28	10.549%	$114.175	$114.18	$114.20	$114.20
Purchase #3	$40.28	4.469%	$42.0801	$42.08	$42.10	$42.10
Purchase #4	$59.91	3.614%	$62.0751	$62.08	$62.10	$62.10
Purchase #5	$229.58	7.193%	$246.0937	$246.09	$246.10	$246.10
Purchase #6	$42.65	6.299%	$45.3365	$45.34	$45.35	$45.30
Purchase #7	$37.78	4.614%	$39.5232	$39.52	$39.50	$39.50
7 purchase totals =	$732.05		$796.5234	$796.53	$796.60	$796.50