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	$92.29	13.579%	$104.8221	$104.82	$104.80	$104.80
Purchase #2	$143.67	4.446%	$150.0576	$150.06	$150.05	$150.10
Purchase #3	$105.46	6.743%	$112.5712	$112.57	$112.55	$112.60
Purchase #4	$23.56	11.136%	$26.1836	$26.18	$26.20	$26.20
Purchase #5	$212.52	6.814%	$227.0011	$227.00	$227.00	$227.00
Purchase #6	$155.54	5.679%	$164.3731	$164.37	$164.35	$164.40
Purchase #7	$164.60	4.579%	$172.137	$172.14	$172.15	$172.10
7 purchase totals =	$897.64		$957.1457	$957.14	$957.10	$957.20