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	$160.58	3.714%	$166.5439	$166.54	$166.55	$166.50
Purchase #2	$191.97	7.528%	$206.4215	$206.42	$206.40	$206.40
Purchase #3	$86.51	5.132%	$90.9497	$90.95	$90.95	$90.90
Purchase #4	$122.67	11.870%	$137.2309	$137.23	$137.25	$137.20
Purchase #5	$172.68	10.356%	$190.5627	$190.56	$190.55	$190.60
Purchase #6	$146.28	11.296%	$162.8038	$162.80	$162.80	$162.80
Purchase #7	$151.86	13.481%	$172.3322	$172.33	$172.35	$172.30
7 purchase totals =	$1,032.55		$1,126.8447	$1,126.83	$1,126.85	$1,126.70