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	$211.42	5.295%	$222.6147	$222.61	$222.60	$222.60
Purchase #2	$47.39	6.342%	$50.3955	$50.40	$50.40	$50.40
Purchase #3	$241.37	8.700%	$262.3692	$262.37	$262.35	$262.40
Purchase #4	$214.89	10.261%	$236.9399	$236.94	$236.95	$236.90
Purchase #5	$61.96	12.250%	$69.5501	$69.55	$69.55	$69.60
Purchase #6	$32.63	4.516%	$34.1036	$34.10	$34.10	$34.10
Purchase #7	$219.90	4.524%	$229.8483	$229.85	$229.85	$229.80
7 purchase totals =	$1,029.56		$1,105.8213	$1,105.82	$1,105.80	$1,105.80