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	$145.97	4.644%	$152.7488	$152.75	$152.75	$152.70
Purchase #2	$81.49	12.128%	$91.3731	$91.37	$91.35	$91.40
Purchase #3	$111.36	11.297%	$123.9403	$123.94	$123.95	$123.90
Purchase #4	$67.85	6.787%	$72.455	$72.46	$72.45	$72.50
Purchase #5	$8.37	9.177%	$9.1381	$9.14	$9.15	$9.10
Purchase #6	$110.97	6.834%	$118.5537	$118.55	$118.55	$118.60
Purchase #7	$172.93	3.607%	$179.1676	$179.17	$179.15	$179.20
7 purchase totals =	$698.94		$747.3766	$747.38	$747.35	$747.40