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	$80.56	7.748%	$86.8018	$86.80	$86.80	$86.80
Purchase #2	$6.78	5.491%	$7.1523	$7.15	$7.15	$7.20
Purchase #3	$228.62	9.707%	$250.8121	$250.81	$250.80	$250.80
Purchase #4	$237.85	3.226%	$245.523	$245.52	$245.50	$245.50
Purchase #5	$87.63	12.368%	$98.4681	$98.47	$98.45	$98.50
Purchase #6	$148.83	11.422%	$165.8294	$165.83	$165.85	$165.80
Purchase #7	$230.64	5.215%	$242.6679	$242.67	$242.65	$242.70
7 purchase totals =	$1,020.91		$1,097.2546	$1,097.25	$1,097.20	$1,097.30