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	$7.59	13.282%	$8.5981	$8.60	$8.60	$8.60
Purchase #2	$44.92	13.162%	$50.8324	$50.83	$50.85	$50.80
Purchase #3	$105.31	3.401%	$108.8916	$108.89	$108.90	$108.90
Purchase #4	$86.52	11.177%	$96.1903	$96.19	$96.20	$96.20
Purchase #5	$94.46	4.489%	$98.7003	$98.70	$98.70	$98.70
Purchase #6	$9.85	6.222%	$10.4629	$10.46	$10.45	$10.50
Purchase #7	$118.46	4.334%	$123.5941	$123.59	$123.60	$123.60
7 purchase totals =	$467.11		$497.2697	$497.26	$497.30	$497.30