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	$43.40	4.389%	$45.3048	$45.30	$45.30	$45.30
Purchase #2	$59.97	10.833%	$66.4666	$66.47	$66.45	$66.50
Purchase #3	$57.63	4.230%	$60.0677	$60.07	$60.05	$60.10
Purchase #4	$143.89	6.871%	$153.7767	$153.78	$153.80	$153.80
Purchase #5	$125.34	7.534%	$134.7831	$134.78	$134.80	$134.80
Purchase #6	$189.67	5.830%	$200.7278	$200.73	$200.75	$200.70
Purchase #7	$11.55	6.492%	$12.2998	$12.30	$12.30	$12.30
7 purchase totals =	$631.45		$673.4265	$673.43	$673.45	$673.50