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	$130.79	13.344%	$148.2426	$148.24	$148.25	$148.20
Purchase #2	$55.99	12.712%	$63.1074	$63.11	$63.10	$63.10
Purchase #3	$211.48	6.616%	$225.4715	$225.47	$225.45	$225.50
Purchase #4	$88.82	13.451%	$100.7672	$100.77	$100.75	$100.80
Purchase #5	$83.89	6.596%	$89.4234	$89.42	$89.40	$89.40
Purchase #6	$128.99	9.423%	$141.1447	$141.14	$141.15	$141.10
Purchase #7	$162.85	8.666%	$176.9626	$176.96	$176.95	$177.00
7 purchase totals =	$862.81		$945.1194	$945.11	$945.05	$945.10