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	$208.94	6.651%	$222.8366	$222.84	$222.85	$222.80
Purchase #2	$220.32	10.784%	$244.0793	$244.08	$244.10	$244.10
Purchase #3	$222.35	12.169%	$249.4078	$249.41	$249.40	$249.40
Purchase #4	$197.86	9.800%	$217.2503	$217.25	$217.25	$217.30
Purchase #5	$174.32	6.167%	$185.0703	$185.07	$185.05	$185.10
Purchase #6	$44.69	11.740%	$49.9366	$49.94	$49.95	$49.90
Purchase #7	$134.83	3.260%	$139.2255	$139.23	$139.25	$139.20
7 purchase totals =	$1,203.31		$1,307.8064	$1,307.82	$1,307.85	$1,307.80