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	$10.80	8.426%	$11.71	$11.71	$11.70	$11.70
Purchase #2	$107.76	3.157%	$111.162	$111.16	$111.15	$111.20
Purchase #3	$134.46	8.690%	$146.1446	$146.14	$146.15	$146.10
Purchase #4	$36.91	3.396%	$38.1635	$38.16	$38.15	$38.20
Purchase #5	$71.60	10.141%	$78.861	$78.86	$78.85	$78.90
Purchase #6	$55.37	12.201%	$62.1257	$62.13	$62.15	$62.10
Purchase #7	$10.89	8.109%	$11.7731	$11.77	$11.75	$11.80
7 purchase totals =	$427.79		$459.9399	$459.93	$459.90	$460.00