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	$229.83	6.174%	$244.0197	$244.02	$244.00	$244.00
Purchase #2	$123.71	11.164%	$137.521	$137.52	$137.50	$137.50
Purchase #3	$231.98	13.852%	$264.1139	$264.11	$264.10	$264.10
Purchase #4	$104.70	6.151%	$111.1401	$111.14	$111.15	$111.10
Purchase #5	$163.32	4.471%	$170.622	$170.62	$170.60	$170.60
Purchase #6	$54.59	9.813%	$59.9469	$59.95	$59.95	$59.90
Purchase #7	$107.29	11.734%	$119.8794	$119.88	$119.90	$119.90
7 purchase totals =	$1,015.42		$1,107.2430	$1,107.24	$1,107.20	$1,107.10