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	$159.79	5.784%	$169.0323	$169.03	$169.05	$169.00
Purchase #2	$47.48	8.710%	$51.6155	$51.62	$51.60	$51.60
Purchase #3	$39.33	4.419%	$41.068	$41.07	$41.05	$41.10
Purchase #4	$37.42	13.106%	$42.3243	$42.32	$42.30	$42.30
Purchase #5	$158.55	6.857%	$169.4218	$169.42	$169.40	$169.40
Purchase #6	$185.35	4.432%	$193.5647	$193.56	$193.55	$193.60
Purchase #7	$81.82	10.783%	$90.6427	$90.64	$90.65	$90.60
7 purchase totals =	$709.74		$757.6693	$757.66	$757.60	$757.60