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	$42.94	7.791%	$46.2855	$46.29	$46.30	$46.30
Purchase #2	$86.63	11.304%	$96.4227	$96.42	$96.40	$96.40
Purchase #3	$49.29	10.674%	$54.5512	$54.55	$54.55	$54.60
Purchase #4	$163.66	5.584%	$172.7988	$172.80	$172.80	$172.80
Purchase #5	$166.37	3.407%	$172.0382	$172.04	$172.05	$172.00
Purchase #6	$223.63	10.559%	$247.2431	$247.24	$247.25	$247.20
Purchase #7	$182.45	7.534%	$196.1958	$196.20	$196.20	$196.20
7 purchase totals =	$914.97		$985.5353	$985.54	$985.55	$985.50