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	$142.89	8.643%	$155.24	$155.24	$155.25	$155.20
Purchase #2	$88.32	10.811%	$97.8683	$97.87	$97.85	$97.90
Purchase #3	$194.51	7.362%	$208.8298	$208.83	$208.85	$208.80
Purchase #4	$54.54	3.468%	$56.4314	$56.43	$56.45	$56.40
Purchase #5	$65.27	11.671%	$72.8877	$72.89	$72.90	$72.90
Purchase #6	$237.82	6.224%	$252.6219	$252.62	$252.60	$252.60
Purchase #7	$233.86	4.482%	$244.3416	$244.34	$244.35	$244.30
7 purchase totals =	$1,017.21		$1,088.2207	$1,088.22	$1,088.25	$1,088.10