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	$208.83	12.226%	$234.3616	$234.36	$234.35	$234.40
Purchase #2	$18.96	13.435%	$21.5073	$21.51	$21.50	$21.50
Purchase #3	$197.55	6.492%	$210.3749	$210.37	$210.35	$210.40
Purchase #4	$248.95	10.187%	$274.3105	$274.31	$274.30	$274.30
Purchase #5	$53.57	6.149%	$56.864	$56.86	$56.85	$56.90
Purchase #6	$118.28	7.547%	$127.2066	$127.21	$127.20	$127.20
Purchase #7	$167.95	4.720%	$175.8772	$175.88	$175.90	$175.90
7 purchase totals =	$1,014.09		$1,100.5021	$1,100.50	$1,100.45	$1,100.60