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	$61.35	10.722%	$67.9279	$67.93	$67.95	$67.90
Purchase #2	$42.71	13.122%	$48.3144	$48.31	$48.30	$48.30
Purchase #3	$236.84	6.754%	$252.8362	$252.84	$252.85	$252.80
Purchase #4	$142.64	11.394%	$158.8924	$158.89	$158.90	$158.90
Purchase #5	$215.97	11.854%	$241.5711	$241.57	$241.55	$241.60
Purchase #6	$212.59	10.198%	$234.2699	$234.27	$234.25	$234.30
Purchase #7	$176.49	9.132%	$192.6071	$192.61	$192.60	$192.60
7 purchase totals =	$1,088.59		$1,196.4190	$1,196.42	$1,196.40	$1,196.40