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	$152.46	8.222%	$164.9953	$165.00	$165.00	$165.00
Purchase #2	$196.49	4.299%	$204.9371	$204.94	$204.95	$204.90
Purchase #3	$179.28	9.659%	$196.5967	$196.60	$196.60	$196.60
Purchase #4	$108.59	7.863%	$117.1284	$117.13	$117.15	$117.10
Purchase #5	$118.46	7.792%	$127.6904	$127.69	$127.70	$127.70
Purchase #6	$160.46	6.190%	$170.3925	$170.39	$170.40	$170.40
Purchase #7	$84.41	8.194%	$91.3266	$91.33	$91.35	$91.30
7 purchase totals =	$1,000.15		$1,073.0670	$1,073.08	$1,073.15	$1,073.00