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	$243.69	4.835%	$255.4724	$255.47	$255.45	$255.50
Purchase #2	$177.53	4.598%	$185.6928	$185.69	$185.70	$185.70
Purchase #3	$112.91	5.240%	$118.8265	$118.83	$118.85	$118.80
Purchase #4	$136.43	12.443%	$153.406	$153.41	$153.40	$153.40
Purchase #5	$85.32	11.615%	$95.2299	$95.23	$95.25	$95.20
Purchase #6	$243.63	3.270%	$251.5967	$251.60	$251.60	$251.60
Purchase #7	$235.39	8.237%	$254.7791	$254.78	$254.80	$254.80
7 purchase totals =	$1,234.90		$1,315.0034	$1,315.01	$1,315.05	$1,315.00