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	$218.66	4.653%	$228.8342	$228.83	$228.85	$228.80
Purchase #2	$54.89	4.651%	$57.4429	$57.44	$57.45	$57.40
Purchase #3	$193.95	10.780%	$214.8578	$214.86	$214.85	$214.90
Purchase #4	$115.52	10.787%	$127.9811	$127.98	$128.00	$128.00
Purchase #5	$100.86	10.790%	$111.7428	$111.74	$111.75	$111.70
Purchase #6	$161.48	11.602%	$180.2149	$180.21	$180.20	$180.20
Purchase #7	$197.60	9.410%	$216.1942	$216.19	$216.20	$216.20
7 purchase totals =	$1,042.96		$1,137.2679	$1,137.25	$1,137.30	$1,137.20