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	$33.40	6.423%	$35.5453	$35.55	$35.55	$35.50
Purchase #2	$178.25	10.563%	$197.0785	$197.08	$197.10	$197.10
Purchase #3	$86.38	13.723%	$98.2339	$98.23	$98.25	$98.20
Purchase #4	$172.35	9.543%	$188.7974	$188.80	$188.80	$188.80
Purchase #5	$193.37	11.626%	$215.8512	$215.85	$215.85	$215.90
Purchase #6	$201.43	6.287%	$214.0939	$214.09	$214.10	$214.10
Purchase #7	$138.58	8.658%	$150.5783	$150.58	$150.60	$150.60
7 purchase totals =	$1,003.76		$1,100.1785	$1,100.18	$1,100.25	$1,100.20