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	$112.43	3.500%	$116.3651	$116.37	$116.35	$116.40
Purchase #2	$96.41	7.196%	$103.3477	$103.35	$103.35	$103.30
Purchase #3	$182.34	13.863%	$207.6178	$207.62	$207.60	$207.60
Purchase #4	$148.84	6.695%	$158.8048	$158.80	$158.80	$158.80
Purchase #5	$107.54	11.140%	$119.52	$119.52	$119.50	$119.50
Purchase #6	$83.69	7.566%	$90.022	$90.02	$90.00	$90.00
Purchase #7	$133.30	11.242%	$148.2856	$148.29	$148.30	$148.30
7 purchase totals =	$864.55		$943.9630	$943.97	$943.90	$943.90