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	$134.53	6.796%	$143.6727	$143.67	$143.65	$143.70
Purchase #2	$65.91	6.221%	$70.0103	$70.01	$70.00	$70.00
Purchase #3	$103.33	11.109%	$114.8089	$114.81	$114.80	$114.80
Purchase #4	$62.27	7.138%	$66.7148	$66.71	$66.70	$66.70
Purchase #5	$69.59	11.201%	$77.3848	$77.38	$77.40	$77.40
Purchase #6	$115.40	10.789%	$127.8505	$127.85	$127.85	$127.90
Purchase #7	$148.78	8.626%	$161.6138	$161.61	$161.60	$161.60
7 purchase totals =	$699.81		$762.0558	$762.04	$762.00	$762.10