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	$57.62	11.617%	$64.3137	$64.31	$64.30	$64.30
Purchase #2	$64.79	11.522%	$72.2551	$72.26	$72.25	$72.30
Purchase #3	$12.34	5.579%	$13.0284	$13.03	$13.05	$13.00
Purchase #4	$205.45	13.601%	$233.3933	$233.39	$233.40	$233.40
Purchase #5	$207.42	5.319%	$218.4527	$218.45	$218.45	$218.50
Purchase #6	$177.46	11.762%	$198.3328	$198.33	$198.35	$198.30
Purchase #7	$193.26	6.274%	$205.3851	$205.39	$205.40	$205.40
7 purchase totals =	$918.34		$1,005.1611	$1,005.16	$1,005.20	$1,005.20