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	$42.46	3.286%	$43.8552	$43.86	$43.85	$43.90
Purchase #2	$250.71	12.752%	$282.6805	$282.68	$282.70	$282.70
Purchase #3	$58.37	11.138%	$64.8713	$64.87	$64.85	$64.90
Purchase #4	$140.49	13.833%	$159.924	$159.92	$159.90	$159.90
Purchase #5	$195.47	11.833%	$218.6	$218.60	$218.60	$218.60
Purchase #6	$194.29	7.592%	$209.0405	$209.04	$209.05	$209.00
Purchase #7	$134.77	13.861%	$153.4505	$153.45	$153.45	$153.50
7 purchase totals =	$1,016.56		$1,132.4220	$1,132.42	$1,132.40	$1,132.50