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	$173.93	12.497%	$195.666	$195.67	$195.65	$195.70
Purchase #2	$182.69	10.743%	$202.3164	$202.32	$202.30	$202.30
Purchase #3	$94.46	5.491%	$99.6468	$99.65	$99.65	$99.60
Purchase #4	$143.76	11.363%	$160.0954	$160.10	$160.10	$160.10
Purchase #5	$224.64	9.422%	$245.8056	$245.81	$245.80	$245.80
Purchase #6	$135.84	4.866%	$142.45	$142.45	$142.45	$142.50
Purchase #7	$38.51	5.485%	$40.6223	$40.62	$40.60	$40.60
7 purchase totals =	$993.83		$1,086.6025	$1,086.62	$1,086.55	$1,086.60