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	$147.48	9.599%	$161.6366	$161.64	$161.65	$161.60
Purchase #2	$50.88	8.414%	$55.161	$55.16	$55.15	$55.20
Purchase #3	$66.41	8.234%	$71.8782	$71.88	$71.90	$71.90
Purchase #4	$103.99	7.525%	$111.8152	$111.82	$111.80	$111.80
Purchase #5	$21.85	7.581%	$23.5064	$23.51	$23.50	$23.50
Purchase #6	$89.65	5.249%	$94.3557	$94.36	$94.35	$94.40
Purchase #7	$101.59	12.790%	$114.5834	$114.58	$114.60	$114.60
7 purchase totals =	$581.85		$632.9365	$632.95	$632.95	$633.00