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	$190.65	8.145%	$206.1784	$206.18	$206.20	$206.20
Purchase #2	$250.40	8.406%	$271.4486	$271.45	$271.45	$271.40
Purchase #3	$70.67	13.377%	$80.1235	$80.12	$80.10	$80.10
Purchase #4	$146.79	6.364%	$156.1317	$156.13	$156.15	$156.10
Purchase #5	$117.99	4.584%	$123.3987	$123.40	$123.40	$123.40
Purchase #6	$124.42	4.168%	$129.6058	$129.61	$129.60	$129.60
Purchase #7	$235.71	8.280%	$255.2268	$255.23	$255.25	$255.20
7 purchase totals =	$1,136.63		$1,222.1135	$1,222.12	$1,222.15	$1,222.00