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	$175.85	8.171%	$190.2187	$190.22	$190.20	$190.20
Purchase #2	$190.31	3.437%	$196.851	$196.85	$196.85	$196.90
Purchase #3	$157.81	4.525%	$164.9509	$164.95	$164.95	$165.00
Purchase #4	$29.65	12.190%	$33.2643	$33.26	$33.25	$33.30
Purchase #5	$112.85	11.627%	$125.9711	$125.97	$125.95	$126.00
Purchase #6	$120.63	5.855%	$127.6929	$127.69	$127.70	$127.70
Purchase #7	$97.59	11.307%	$108.6245	$108.62	$108.60	$108.60
7 purchase totals =	$884.69		$947.5734	$947.56	$947.50	$947.70