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	$220.27	7.358%	$236.4775	$236.48	$236.50	$236.50
Purchase #2	$64.69	11.509%	$72.1352	$72.14	$72.15	$72.10
Purchase #3	$216.74	7.621%	$233.2578	$233.26	$233.25	$233.30
Purchase #4	$97.70	5.115%	$102.6974	$102.70	$102.70	$102.70
Purchase #5	$191.76	10.345%	$211.5976	$211.60	$211.60	$211.60
Purchase #6	$164.90	10.451%	$182.1337	$182.13	$182.15	$182.10
Purchase #7	$37.66	4.822%	$39.476	$39.48	$39.50	$39.50
7 purchase totals =	$993.72		$1,077.7752	$1,077.79	$1,077.85	$1,077.80