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	$129.51	10.797%	$143.4932	$143.49	$143.50	$143.50
Purchase #2	$149.28	6.448%	$158.9056	$158.91	$158.90	$158.90
Purchase #3	$129.97	11.238%	$144.576	$144.58	$144.60	$144.60
Purchase #4	$153.57	9.411%	$168.0225	$168.02	$168.00	$168.00
Purchase #5	$70.72	7.740%	$76.1937	$76.19	$76.20	$76.20
Purchase #6	$59.59	9.167%	$65.0526	$65.05	$65.05	$65.10
Purchase #7	$175.89	5.131%	$184.9149	$184.91	$184.90	$184.90
7 purchase totals =	$868.53		$941.1585	$941.15	$941.15	$941.20