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	$241.84	11.402%	$269.4146	$269.41	$269.40	$269.40
Purchase #2	$107.44	3.858%	$111.585	$111.59	$111.60	$111.60
Purchase #3	$145.25	11.873%	$162.4955	$162.50	$162.50	$162.50
Purchase #4	$12.69	8.489%	$13.7673	$13.77	$13.75	$13.80
Purchase #5	$9.25	12.306%	$10.3883	$10.39	$10.40	$10.40
Purchase #6	$220.29	9.854%	$241.9974	$242.00	$242.00	$242.00
Purchase #7	$111.77	5.812%	$118.2661	$118.27	$118.25	$118.30
7 purchase totals =	$848.53		$927.9142	$927.93	$927.90	$928.00