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	$181.90	3.406%	$188.0955	$188.10	$188.10	$188.10
Purchase #2	$86.30	9.830%	$94.7833	$94.78	$94.80	$94.80
Purchase #3	$20.32	13.626%	$23.0888	$23.09	$23.10	$23.10
Purchase #4	$211.96	10.209%	$233.599	$233.60	$233.60	$233.60
Purchase #5	$18.73	13.635%	$21.2838	$21.28	$21.30	$21.30
Purchase #6	$67.66	7.823%	$72.953	$72.95	$72.95	$73.00
Purchase #7	$96.43	7.421%	$103.5861	$103.59	$103.60	$103.60
7 purchase totals =	$683.30		$737.3895	$737.39	$737.45	$737.50