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	$146.53	11.168%	$162.8945	$162.89	$162.90	$162.90
Purchase #2	$66.83	7.686%	$71.9666	$71.97	$71.95	$72.00
Purchase #3	$94.76	13.427%	$107.4834	$107.48	$107.50	$107.50
Purchase #4	$128.44	11.572%	$143.3031	$143.30	$143.30	$143.30
Purchase #5	$90.37	13.596%	$102.6567	$102.66	$102.65	$102.70
Purchase #6	$111.51	4.856%	$116.9249	$116.92	$116.90	$116.90
Purchase #7	$243.27	9.700%	$266.8672	$266.87	$266.85	$266.90
7 purchase totals =	$881.71		$972.0964	$972.09	$972.05	$972.20