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	$95.42	10.430%	$105.3723	$105.37	$105.35	$105.40
Purchase #2	$125.29	4.653%	$131.1197	$131.12	$131.10	$131.10
Purchase #3	$44.83	3.571%	$46.4309	$46.43	$46.45	$46.40
Purchase #4	$56.59	7.671%	$60.931	$60.93	$60.95	$60.90
Purchase #5	$138.42	9.264%	$151.2432	$151.24	$151.25	$151.20
Purchase #6	$51.72	12.782%	$58.3309	$58.33	$58.35	$58.30
Purchase #7	$183.43	4.273%	$191.268	$191.27	$191.25	$191.30
7 purchase totals =	$695.70		$744.6960	$744.69	$744.70	$744.60