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	$164.60	3.179%	$169.8326	$169.83	$169.85	$169.80
Purchase #2	$187.95	6.430%	$200.0352	$200.04	$200.05	$200.00
Purchase #3	$105.89	3.510%	$109.6067	$109.61	$109.60	$109.60
Purchase #4	$53.88	11.622%	$60.1419	$60.14	$60.15	$60.10
Purchase #5	$92.77	9.525%	$101.6063	$101.61	$101.60	$101.60
Purchase #6	$96.46	13.358%	$109.3451	$109.35	$109.35	$109.30
Purchase #7	$130.44	13.848%	$148.5033	$148.50	$148.50	$148.50
7 purchase totals =	$831.99		$899.0711	$899.08	$899.10	$898.90