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	$143.83	4.509%	$150.3153	$150.32	$150.30	$150.30
Purchase #2	$224.50	8.629%	$243.8721	$243.87	$243.85	$243.90
Purchase #3	$130.83	10.551%	$144.6339	$144.63	$144.65	$144.60
Purchase #4	$175.72	5.598%	$185.5568	$185.56	$185.55	$185.60
Purchase #5	$236.70	4.646%	$247.6971	$247.70	$247.70	$247.70
Purchase #6	$124.66	9.769%	$136.838	$136.84	$136.85	$136.80
Purchase #7	$187.64	4.730%	$196.5154	$196.52	$196.50	$196.50
7 purchase totals =	$1,223.88		$1,305.4286	$1,305.44	$1,305.40	$1,305.40