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	$61.32	3.752%	$63.6207	$63.62	$63.60	$63.60
Purchase #2	$42.44	4.161%	$44.2059	$44.21	$44.20	$44.20
Purchase #3	$206.72	8.116%	$223.4974	$223.50	$223.50	$223.50
Purchase #4	$218.30	10.748%	$241.7629	$241.76	$241.75	$241.80
Purchase #5	$86.60	4.362%	$90.3775	$90.38	$90.40	$90.40
Purchase #6	$153.27	11.241%	$170.4991	$170.50	$170.50	$170.50
Purchase #7	$17.60	10.122%	$19.3815	$19.38	$19.40	$19.40
7 purchase totals =	$786.25		$853.3450	$853.35	$853.35	$853.40