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	$92.50	3.536%	$95.7708	$95.77	$95.75	$95.80
Purchase #2	$132.80	13.669%	$150.9524	$150.95	$150.95	$151.00
Purchase #3	$14.91	10.139%	$16.4217	$16.42	$16.40	$16.40
Purchase #4	$115.42	10.817%	$127.905	$127.91	$127.90	$127.90
Purchase #5	$68.96	12.500%	$77.58	$77.58	$77.60	$77.60
Purchase #6	$91.38	10.780%	$101.2308	$101.23	$101.25	$101.20
Purchase #7	$41.52	8.512%	$45.0542	$45.05	$45.05	$45.10
7 purchase totals =	$557.49		$614.9149	$614.91	$614.90	$615.00