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	$215.28	4.321%	$224.5822	$224.58	$224.60	$224.60
Purchase #2	$216.49	11.339%	$241.0378	$241.04	$241.05	$241.00
Purchase #3	$69.57	12.169%	$78.036	$78.04	$78.05	$78.00
Purchase #4	$136.68	10.653%	$151.2405	$151.24	$151.25	$151.20
Purchase #5	$104.40	5.355%	$109.9906	$109.99	$110.00	$110.00
Purchase #6	$68.31	6.149%	$72.5104	$72.51	$72.50	$72.50
Purchase #7	$96.30	7.515%	$103.5369	$103.54	$103.55	$103.50
7 purchase totals =	$907.03		$980.9344	$980.94	$981.00	$980.80