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	$65.89	9.381%	$72.0711	$72.07	$72.05	$72.10
Purchase #2	$114.90	12.144%	$128.8535	$128.85	$128.85	$128.90
Purchase #3	$213.41	7.227%	$228.8331	$228.83	$228.85	$228.80
Purchase #4	$66.41	6.233%	$70.5493	$70.55	$70.55	$70.50
Purchase #5	$112.70	13.224%	$127.6034	$127.60	$127.60	$127.60
Purchase #6	$67.83	10.811%	$75.1631	$75.16	$75.15	$75.20
Purchase #7	$155.55	8.477%	$168.736	$168.74	$168.75	$168.70
7 purchase totals =	$796.69		$871.8095	$871.80	$871.80	$871.80