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	$85.29	5.159%	$89.6901	$89.69	$89.70	$89.70
Purchase #2	$67.82	6.191%	$72.0187	$72.02	$72.00	$72.00
Purchase #3	$98.83	12.647%	$111.329	$111.33	$111.35	$111.30
Purchase #4	$241.78	7.788%	$260.6098	$260.61	$260.60	$260.60
Purchase #5	$228.84	10.366%	$252.5616	$252.56	$252.55	$252.60
Purchase #6	$52.44	10.864%	$58.1371	$58.14	$58.15	$58.10
Purchase #7	$246.38	5.555%	$260.0664	$260.07	$260.05	$260.10
7 purchase totals =	$1,021.38		$1,104.4127	$1,104.42	$1,104.40	$1,104.40