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	$232.41	12.124%	$260.5874	$260.59	$260.60	$260.60
Purchase #2	$173.35	4.491%	$181.1351	$181.14	$181.15	$181.10
Purchase #3	$209.49	7.588%	$225.3861	$225.39	$225.40	$225.40
Purchase #4	$192.28	10.330%	$212.1425	$212.14	$212.15	$212.10
Purchase #5	$123.90	7.257%	$132.8914	$132.89	$132.90	$132.90
Purchase #6	$109.63	13.611%	$124.5517	$124.55	$124.55	$124.60
Purchase #7	$114.50	11.456%	$127.6171	$127.62	$127.60	$127.60
7 purchase totals =	$1,155.56		$1,264.3113	$1,264.32	$1,264.35	$1,264.30