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	$204.75	10.185%	$225.6038	$225.60	$225.60	$225.60
Purchase #2	$193.62	12.649%	$218.111	$218.11	$218.10	$218.10
Purchase #3	$215.91	10.615%	$238.8288	$238.83	$238.85	$238.80
Purchase #4	$123.71	4.228%	$128.9405	$128.94	$128.95	$128.90
Purchase #5	$164.47	13.862%	$187.2688	$187.27	$187.25	$187.30
Purchase #6	$233.52	3.445%	$241.5648	$241.56	$241.55	$241.60
Purchase #7	$92.82	8.204%	$100.435	$100.44	$100.45	$100.40
7 purchase totals =	$1,228.80		$1,340.7527	$1,340.75	$1,340.75	$1,340.70