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	$110.79	13.746%	$126.0192	$126.02	$126.00	$126.00
Purchase #2	$18.99	5.346%	$20.0052	$20.01	$20.00	$20.00
Purchase #3	$117.92	12.790%	$133.002	$133.00	$133.00	$133.00
Purchase #4	$61.52	9.137%	$67.1411	$67.14	$67.15	$67.10
Purchase #5	$13.95	8.219%	$15.0966	$15.10	$15.10	$15.10
Purchase #6	$158.55	8.679%	$172.3106	$172.31	$172.30	$172.30
Purchase #7	$37.68	11.523%	$42.0219	$42.02	$42.00	$42.00
7 purchase totals =	$519.40		$575.5966	$575.60	$575.55	$575.50