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	$196.59	13.233%	$222.6048	$222.60	$222.60	$222.60
Purchase #2	$21.32	10.659%	$23.5925	$23.59	$23.60	$23.60
Purchase #3	$187.83	13.333%	$212.8734	$212.87	$212.85	$212.90
Purchase #4	$96.82	10.291%	$106.7837	$106.78	$106.80	$106.80
Purchase #5	$94.95	9.497%	$103.9674	$103.97	$103.95	$104.00
Purchase #6	$150.74	13.788%	$171.524	$171.52	$171.50	$171.50
Purchase #7	$31.86	3.426%	$32.9515	$32.95	$32.95	$33.00
7 purchase totals =	$780.11		$874.2973	$874.28	$874.25	$874.40