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	$61.61	9.809%	$67.6533	$67.65	$67.65	$67.70
Purchase #2	$24.41	11.422%	$27.1981	$27.20	$27.20	$27.20
Purchase #3	$163.55	12.644%	$184.2293	$184.23	$184.25	$184.20
Purchase #4	$215.57	10.448%	$238.0928	$238.09	$238.10	$238.10
Purchase #5	$123.60	3.437%	$127.8481	$127.85	$127.85	$127.80
Purchase #6	$154.61	7.151%	$165.6662	$165.67	$165.65	$165.70
Purchase #7	$60.46	12.343%	$67.9226	$67.92	$67.90	$67.90
7 purchase totals =	$803.81		$878.6104	$878.61	$878.60	$878.60