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	$36.75	10.670%	$40.6712	$40.67	$40.65	$40.70
Purchase #2	$28.52	10.855%	$31.6158	$31.62	$31.60	$31.60
Purchase #3	$149.35	8.744%	$162.4092	$162.41	$162.40	$162.40
Purchase #4	$77.43	7.786%	$83.4587	$83.46	$83.45	$83.50
Purchase #5	$152.28	8.205%	$164.7746	$164.77	$164.75	$164.80
Purchase #6	$150.78	5.143%	$158.5346	$158.53	$158.55	$158.50
Purchase #7	$122.42	4.344%	$127.7379	$127.74	$127.75	$127.70
7 purchase totals =	$717.53		$769.2020	$769.20	$769.15	$769.20