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	$95.69	9.389%	$104.6743	$104.67	$104.65	$104.70
Purchase #2	$151.44	7.535%	$162.851	$162.85	$162.85	$162.90
Purchase #3	$89.40	12.655%	$100.7136	$100.71	$100.70	$100.70
Purchase #4	$144.62	12.321%	$162.4386	$162.44	$162.45	$162.40
Purchase #5	$49.38	9.829%	$54.2336	$54.23	$54.25	$54.20
Purchase #6	$29.54	4.248%	$30.7949	$30.79	$30.80	$30.80
Purchase #7	$239.55	13.486%	$271.8557	$271.86	$271.85	$271.90
7 purchase totals =	$799.62		$887.5617	$887.55	$887.55	$887.60