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	$184.41	6.736%	$196.8319	$196.83	$196.85	$196.80
Purchase #2	$123.91	8.446%	$134.3754	$134.38	$134.40	$134.40
Purchase #3	$156.79	7.577%	$168.67	$168.67	$168.65	$168.70
Purchase #4	$20.52	3.763%	$21.2922	$21.29	$21.30	$21.30
Purchase #5	$38.64	10.797%	$42.812	$42.81	$42.80	$42.80
Purchase #6	$117.27	3.630%	$121.5269	$121.53	$121.55	$121.50
Purchase #7	$28.75	10.488%	$31.7653	$31.77	$31.75	$31.80
7 purchase totals =	$670.29		$717.2737	$717.28	$717.30	$717.30