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	$183.98	7.622%	$198.003	$198.00	$198.00	$198.00
Purchase #2	$197.66	9.149%	$215.7439	$215.74	$215.75	$215.70
Purchase #3	$150.42	4.643%	$157.404	$157.40	$157.40	$157.40
Purchase #4	$44.28	7.550%	$47.6231	$47.62	$47.60	$47.60
Purchase #5	$168.71	4.625%	$176.5128	$176.51	$176.50	$176.50
Purchase #6	$85.47	4.699%	$89.4862	$89.49	$89.50	$89.50
Purchase #7	$90.65	10.824%	$100.462	$100.46	$100.45	$100.50
7 purchase totals =	$921.17		$985.2350	$985.22	$985.20	$985.20