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	$44.79	3.857%	$46.5176	$46.52	$46.50	$46.50
Purchase #2	$54.85	11.500%	$61.1578	$61.16	$61.15	$61.20
Purchase #3	$10.97	5.304%	$11.5518	$11.55	$11.55	$11.60
Purchase #4	$47.66	10.559%	$52.6924	$52.69	$52.70	$52.70
Purchase #5	$129.76	13.544%	$147.3347	$147.33	$147.35	$147.30
Purchase #6	$127.27	13.555%	$144.5214	$144.52	$144.50	$144.50
Purchase #7	$234.67	13.587%	$266.5546	$266.55	$266.55	$266.60
7 purchase totals =	$649.97		$730.3303	$730.32	$730.30	$730.40