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	$188.49	12.670%	$212.3717	$212.37	$212.35	$212.40
Purchase #2	$132.26	5.244%	$139.1957	$139.20	$139.20	$139.20
Purchase #3	$63.33	11.160%	$70.3976	$70.40	$70.40	$70.40
Purchase #4	$152.72	8.826%	$166.1991	$166.20	$166.20	$166.20
Purchase #5	$32.65	9.151%	$35.6378	$35.64	$35.65	$35.60
Purchase #6	$184.67	6.376%	$196.4446	$196.44	$196.45	$196.40
Purchase #7	$27.57	3.744%	$28.6022	$28.60	$28.60	$28.60
7 purchase totals =	$781.69		$848.8487	$848.85	$848.85	$848.80