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	$156.78	7.192%	$168.0556	$168.06	$168.05	$168.10
Purchase #2	$216.42	9.811%	$237.653	$237.65	$237.65	$237.70
Purchase #3	$112.68	6.380%	$119.869	$119.87	$119.85	$119.90
Purchase #4	$103.27	11.760%	$115.4146	$115.41	$115.40	$115.40
Purchase #5	$179.94	11.135%	$199.9763	$199.98	$200.00	$200.00
Purchase #6	$159.58	8.172%	$172.6209	$172.62	$172.60	$172.60
Purchase #7	$146.39	4.249%	$152.6101	$152.61	$152.60	$152.60
7 purchase totals =	$1,075.06		$1,166.1995	$1,166.20	$1,166.15	$1,166.30