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	$102.85	8.246%	$111.331	$111.33	$111.35	$111.30
Purchase #2	$7.99	13.508%	$9.0693	$9.07	$9.05	$9.10
Purchase #3	$151.77	8.226%	$164.2546	$164.25	$164.25	$164.30
Purchase #4	$38.40	12.770%	$43.3037	$43.30	$43.30	$43.30
Purchase #5	$147.87	5.667%	$156.2498	$156.25	$156.25	$156.20
Purchase #6	$80.76	5.869%	$85.4998	$85.50	$85.50	$85.50
Purchase #7	$143.75	6.527%	$153.1326	$153.13	$153.15	$153.10
7 purchase totals =	$673.39		$722.8408	$722.83	$722.85	$722.80