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	$204.43	9.507%	$223.8652	$223.87	$223.85	$223.90
Purchase #2	$52.31	4.218%	$54.5164	$54.52	$54.50	$54.50
Purchase #3	$77.92	10.215%	$85.8795	$85.88	$85.90	$85.90
Purchase #4	$23.41	6.353%	$24.8972	$24.90	$24.90	$24.90
Purchase #5	$87.70	4.528%	$91.6711	$91.67	$91.65	$91.70
Purchase #6	$250.27	4.725%	$262.0953	$262.10	$262.10	$262.10
Purchase #7	$176.51	5.241%	$185.7609	$185.76	$185.75	$185.80
7 purchase totals =	$872.55		$928.6856	$928.70	$928.65	$928.80