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	$210.48	8.862%	$229.1327	$229.13	$229.15	$229.10
Purchase #2	$177.38	4.612%	$185.5608	$185.56	$185.55	$185.60
Purchase #3	$244.42	4.619%	$255.7098	$255.71	$255.70	$255.70
Purchase #4	$152.92	3.285%	$157.9434	$157.94	$157.95	$157.90
Purchase #5	$243.91	4.776%	$255.5591	$255.56	$255.55	$255.60
Purchase #6	$111.25	5.705%	$117.5968	$117.60	$117.60	$117.60
Purchase #7	$65.89	4.516%	$68.8656	$68.87	$68.85	$68.90
7 purchase totals =	$1,206.25		$1,270.3682	$1,270.37	$1,270.35	$1,270.40