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	$14.67	12.227%	$16.4637	$16.46	$16.45	$16.50
Purchase #2	$80.94	13.274%	$91.684	$91.68	$91.70	$91.70
Purchase #3	$67.54	4.577%	$70.6313	$70.63	$70.65	$70.60
Purchase #4	$9.80	5.761%	$10.3646	$10.36	$10.35	$10.40
Purchase #5	$42.55	9.235%	$46.4795	$46.48	$46.50	$46.50
Purchase #6	$140.50	10.744%	$155.5953	$155.60	$155.60	$155.60
Purchase #7	$81.42	10.392%	$89.8812	$89.88	$89.90	$89.90
7 purchase totals =	$437.42		$481.0996	$481.09	$481.15	$481.20