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	$166.28	7.628%	$178.9638	$178.96	$178.95	$179.00
Purchase #2	$184.80	6.324%	$196.4868	$196.49	$196.50	$196.50
Purchase #3	$7.35	7.651%	$7.9123	$7.91	$7.90	$7.90
Purchase #4	$173.73	3.107%	$179.1278	$179.13	$179.15	$179.10
Purchase #5	$38.41	4.774%	$40.2437	$40.24	$40.25	$40.20
Purchase #6	$55.71	9.264%	$60.871	$60.87	$60.85	$60.90
Purchase #7	$100.79	13.631%	$114.5287	$114.53	$114.55	$114.50
7 purchase totals =	$727.07		$778.1341	$778.13	$778.15	$778.10