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	$145.58	10.814%	$161.323	$161.32	$161.30	$161.30
Purchase #2	$41.91	8.143%	$45.3227	$45.32	$45.30	$45.30
Purchase #3	$44.27	3.554%	$45.8434	$45.84	$45.85	$45.80
Purchase #4	$68.25	4.179%	$71.1022	$71.10	$71.10	$71.10
Purchase #5	$30.60	3.326%	$31.6178	$31.62	$31.60	$31.60
Purchase #6	$187.65	5.231%	$197.466	$197.47	$197.45	$197.50
Purchase #7	$72.87	10.476%	$80.5039	$80.50	$80.50	$80.50
7 purchase totals =	$591.13		$633.1790	$633.17	$633.10	$633.10