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	$242.84	5.594%	$256.4245	$256.42	$256.40	$256.40
Purchase #2	$61.83	12.429%	$69.5149	$69.51	$69.50	$69.50
Purchase #3	$221.88	8.294%	$240.2827	$240.28	$240.30	$240.30
Purchase #4	$27.67	10.214%	$30.4962	$30.50	$30.50	$30.50
Purchase #5	$54.27	4.735%	$56.8397	$56.84	$56.85	$56.80
Purchase #6	$118.59	7.522%	$127.5103	$127.51	$127.50	$127.50
Purchase #7	$181.76	12.753%	$204.9399	$204.94	$204.95	$204.90
7 purchase totals =	$908.84		$986.0082	$986.00	$986.00	$985.90