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	$97.53	10.314%	$107.5892	$107.59	$107.60	$107.60
Purchase #2	$25.80	9.663%	$28.2931	$28.29	$28.30	$28.30
Purchase #3	$90.89	3.476%	$94.0493	$94.05	$94.05	$94.00
Purchase #4	$87.54	10.218%	$96.4848	$96.48	$96.50	$96.50
Purchase #5	$14.86	4.247%	$15.4911	$15.49	$15.50	$15.50
Purchase #6	$79.58	5.448%	$83.9155	$83.92	$83.90	$83.90
Purchase #7	$132.34	13.804%	$150.6082	$150.61	$150.60	$150.60
7 purchase totals =	$528.54		$576.4312	$576.43	$576.45	$576.40