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	$219.33	4.785%	$229.8249	$229.82	$229.80	$229.80
Purchase #2	$18.73	13.297%	$21.2205	$21.22	$21.20	$21.20
Purchase #3	$19.47	5.113%	$20.4655	$20.47	$20.45	$20.50
Purchase #4	$48.91	4.527%	$51.1242	$51.12	$51.10	$51.10
Purchase #5	$91.25	13.804%	$103.8462	$103.85	$103.85	$103.80
Purchase #6	$203.69	6.255%	$216.4308	$216.43	$216.45	$216.40
Purchase #7	$35.43	3.250%	$36.5815	$36.58	$36.60	$36.60
7 purchase totals =	$636.81		$679.4936	$679.49	$679.45	$679.40