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	$222.58	5.641%	$235.1357	$235.14	$235.15	$235.10
Purchase #2	$222.96	10.291%	$245.9048	$245.90	$245.90	$245.90
Purchase #3	$157.33	13.853%	$179.1249	$179.12	$179.10	$179.10
Purchase #4	$147.39	4.125%	$153.4698	$153.47	$153.45	$153.50
Purchase #5	$163.40	6.181%	$173.4998	$173.50	$173.50	$173.50
Purchase #6	$104.62	11.447%	$116.5959	$116.60	$116.60	$116.60
Purchase #7	$19.32	6.217%	$20.5211	$20.52	$20.50	$20.50
7 purchase totals =	$1,037.60		$1,124.2520	$1,124.25	$1,124.20	$1,124.20