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	$226.51	6.422%	$241.0565	$241.06	$241.05	$241.10
Purchase #2	$78.28	5.555%	$82.6285	$82.63	$82.65	$82.60
Purchase #3	$148.87	9.434%	$162.9144	$162.91	$162.90	$162.90
Purchase #4	$244.59	9.510%	$267.8505	$267.85	$267.85	$267.90
Purchase #5	$41.63	4.351%	$43.4413	$43.44	$43.45	$43.40
Purchase #6	$233.58	13.412%	$264.9077	$264.91	$264.90	$264.90
Purchase #7	$134.96	10.216%	$148.7475	$148.75	$148.75	$148.70
7 purchase totals =	$1,108.42		$1,211.5464	$1,211.55	$1,211.55	$1,211.50