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	$224.47	10.523%	$248.091	$248.09	$248.10	$248.10
Purchase #2	$146.47	7.123%	$156.9031	$156.90	$156.90	$156.90
Purchase #3	$148.69	13.199%	$168.3156	$168.32	$168.30	$168.30
Purchase #4	$116.56	8.539%	$126.5131	$126.51	$126.50	$126.50
Purchase #5	$182.74	7.700%	$196.811	$196.81	$196.80	$196.80
Purchase #6	$118.66	11.618%	$132.4459	$132.45	$132.45	$132.40
Purchase #7	$13.76	9.333%	$15.0442	$15.04	$15.05	$15.00
7 purchase totals =	$951.35		$1,044.1239	$1,044.12	$1,044.10	$1,044.00