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	$60.40	11.495%	$67.343	$67.34	$67.35	$67.30
Purchase #2	$70.60	9.152%	$77.0613	$77.06	$77.05	$77.10
Purchase #3	$160.25	4.286%	$167.1183	$167.12	$167.10	$167.10
Purchase #4	$206.87	7.566%	$222.5218	$222.52	$222.50	$222.50
Purchase #5	$152.78	3.426%	$158.0142	$158.01	$158.00	$158.00
Purchase #6	$61.93	9.202%	$67.6288	$67.63	$67.65	$67.60
Purchase #7	$56.40	9.383%	$61.692	$61.69	$61.70	$61.70
7 purchase totals =	$769.23		$821.3794	$821.37	$821.35	$821.30