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	$246.90	4.750%	$258.6278	$258.63	$258.65	$258.60
Purchase #2	$165.66	4.654%	$173.3698	$173.37	$173.35	$173.40
Purchase #3	$100.46	11.120%	$111.6312	$111.63	$111.65	$111.60
Purchase #4	$138.78	8.469%	$150.5333	$150.53	$150.55	$150.50
Purchase #5	$71.85	12.464%	$80.8054	$80.81	$80.80	$80.80
Purchase #6	$115.99	4.131%	$120.7815	$120.78	$120.80	$120.80
Purchase #7	$92.53	13.706%	$105.2122	$105.21	$105.20	$105.20
7 purchase totals =	$932.17		$1,000.9612	$1,000.96	$1,001.00	$1,000.90