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	$12.68	10.341%	$13.9912	$13.99	$14.00	$14.00
Purchase #2	$182.69	7.575%	$196.5288	$196.53	$196.55	$196.50
Purchase #3	$199.42	12.403%	$224.1541	$224.15	$224.15	$224.20
Purchase #4	$90.52	5.488%	$95.4877	$95.49	$95.50	$95.50
Purchase #5	$83.66	7.631%	$90.0441	$90.04	$90.05	$90.00
Purchase #6	$72.95	13.589%	$82.8632	$82.86	$82.85	$82.90
Purchase #7	$209.56	12.863%	$236.5157	$236.52	$236.50	$236.50
7 purchase totals =	$851.48		$939.5848	$939.58	$939.60	$939.60