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	$100.25	3.201%	$103.459	$103.46	$103.45	$103.50
Purchase #2	$106.50	9.643%	$116.7698	$116.77	$116.75	$116.80
Purchase #3	$9.53	11.109%	$10.5887	$10.59	$10.60	$10.60
Purchase #4	$20.84	3.461%	$21.5613	$21.56	$21.55	$21.60
Purchase #5	$212.36	12.171%	$238.2063	$238.21	$238.20	$238.20
Purchase #6	$47.58	6.791%	$50.8112	$50.81	$50.80	$50.80
Purchase #7	$181.31	5.264%	$190.8542	$190.85	$190.85	$190.90
7 purchase totals =	$678.37		$732.2505	$732.25	$732.20	$732.40