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	$105.73	5.437%	$111.4785	$111.48	$111.50	$111.50
Purchase #2	$67.40	8.764%	$73.3069	$73.31	$73.30	$73.30
Purchase #3	$18.76	3.199%	$19.3601	$19.36	$19.35	$19.40
Purchase #4	$44.97	12.559%	$50.6178	$50.62	$50.60	$50.60
Purchase #5	$130.35	6.537%	$138.871	$138.87	$138.85	$138.90
Purchase #6	$126.64	11.126%	$140.73	$140.73	$140.75	$140.70
Purchase #7	$169.65	5.189%	$178.4531	$178.45	$178.45	$178.50
7 purchase totals =	$663.50		$712.8174	$712.82	$712.80	$712.90