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	$19.56	5.523%	$20.6403	$20.64	$20.65	$20.60
Purchase #2	$42.89	5.746%	$45.3545	$45.35	$45.35	$45.40
Purchase #3	$156.99	7.405%	$168.6151	$168.62	$168.60	$168.60
Purchase #4	$178.66	8.256%	$193.4102	$193.41	$193.40	$193.40
Purchase #5	$237.68	6.196%	$252.4067	$252.41	$252.40	$252.40
Purchase #6	$204.32	11.212%	$227.2284	$227.23	$227.25	$227.20
Purchase #7	$211.75	5.675%	$223.7668	$223.77	$223.75	$223.80
7 purchase totals =	$1,051.85		$1,131.4220	$1,131.43	$1,131.40	$1,131.40