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	$205.64	8.379%	$222.8706	$222.87	$222.85	$222.90
Purchase #2	$175.50	5.687%	$185.4807	$185.48	$185.50	$185.50
Purchase #3	$152.87	12.610%	$172.1469	$172.15	$172.15	$172.10
Purchase #4	$108.82	8.114%	$117.6497	$117.65	$117.65	$117.60
Purchase #5	$64.71	8.743%	$70.3676	$70.37	$70.35	$70.40
Purchase #6	$51.33	6.824%	$54.8328	$54.83	$54.85	$54.80
Purchase #7	$72.97	11.627%	$81.4542	$81.45	$81.45	$81.50
7 purchase totals =	$831.84		$904.8025	$904.80	$904.80	$904.80