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	$158.86	6.862%	$169.761	$169.76	$169.75	$169.80
Purchase #2	$116.34	9.701%	$127.6261	$127.63	$127.65	$127.60
Purchase #3	$248.31	4.522%	$259.5386	$259.54	$259.55	$259.50
Purchase #4	$126.48	3.839%	$131.3356	$131.34	$131.35	$131.30
Purchase #5	$20.73	10.317%	$22.8687	$22.87	$22.85	$22.90
Purchase #6	$236.60	12.852%	$267.0078	$267.01	$267.00	$267.00
Purchase #7	$116.68	5.630%	$123.2491	$123.25	$123.25	$123.20
7 purchase totals =	$1,024.00		$1,101.3869	$1,101.40	$1,101.40	$1,101.30