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	$217.51	6.450%	$231.5394	$231.54	$231.55	$231.50
Purchase #2	$50.27	5.442%	$53.0057	$53.01	$53.00	$53.00
Purchase #3	$241.98	5.611%	$255.5575	$255.56	$255.55	$255.60
Purchase #4	$235.96	12.190%	$264.7235	$264.72	$264.70	$264.70
Purchase #5	$100.34	11.782%	$112.1621	$112.16	$112.15	$112.20
Purchase #6	$50.77	10.757%	$56.2313	$56.23	$56.25	$56.20
Purchase #7	$128.32	8.207%	$138.8512	$138.85	$138.85	$138.90
7 purchase totals =	$1,025.15		$1,112.0707	$1,112.07	$1,112.05	$1,112.10