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	$183.89	12.677%	$207.2017	$207.20	$207.20	$207.20
Purchase #2	$44.97	13.172%	$50.8934	$50.89	$50.90	$50.90
Purchase #3	$217.32	5.657%	$229.6138	$229.61	$229.60	$229.60
Purchase #4	$137.89	3.564%	$142.8044	$142.80	$142.80	$142.80
Purchase #5	$111.42	6.691%	$118.8751	$118.88	$118.90	$118.90
Purchase #6	$249.61	5.728%	$263.9077	$263.91	$263.90	$263.90
Purchase #7	$155.26	8.765%	$168.8685	$168.87	$168.85	$168.90
7 purchase totals =	$1,100.36		$1,182.1646	$1,182.16	$1,182.15	$1,182.20