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	$58.73	13.713%	$66.7836	$66.78	$66.80	$66.80
Purchase #2	$86.54	13.172%	$97.939	$97.94	$97.95	$97.90
Purchase #3	$133.99	13.341%	$151.8656	$151.87	$151.85	$151.90
Purchase #4	$202.77	12.271%	$227.6519	$227.65	$227.65	$227.70
Purchase #5	$128.81	9.867%	$141.5197	$141.52	$141.50	$141.50
Purchase #6	$150.52	5.566%	$158.8979	$158.90	$158.90	$158.90
Purchase #7	$229.91	8.560%	$249.5903	$249.59	$249.60	$249.60
7 purchase totals =	$991.27		$1,094.2480	$1,094.25	$1,094.25	$1,094.30