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	$56.27	9.156%	$61.4221	$61.42	$61.40	$61.40
Purchase #2	$60.60	7.112%	$64.9099	$64.91	$64.90	$64.90
Purchase #3	$200.89	6.739%	$214.428	$214.43	$214.45	$214.40
Purchase #4	$83.85	13.307%	$95.0079	$95.01	$95.00	$95.00
Purchase #5	$91.96	6.670%	$98.0937	$98.09	$98.10	$98.10
Purchase #6	$64.43	8.165%	$69.6907	$69.69	$69.70	$69.70
Purchase #7	$173.32	6.454%	$184.5061	$184.51	$184.50	$184.50
7 purchase totals =	$731.32		$788.0584	$788.06	$788.05	$788.00