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	$205.52	8.458%	$222.9029	$222.90	$222.90	$222.90
Purchase #2	$187.33	3.293%	$193.4988	$193.50	$193.50	$193.50
Purchase #3	$141.61	6.358%	$150.6136	$150.61	$150.60	$150.60
Purchase #4	$92.44	11.278%	$102.8654	$102.87	$102.85	$102.90
Purchase #5	$46.54	5.869%	$49.2714	$49.27	$49.25	$49.30
Purchase #6	$107.75	6.246%	$114.4801	$114.48	$114.50	$114.50
Purchase #7	$19.42	7.534%	$20.8831	$20.88	$20.90	$20.90
7 purchase totals =	$800.61		$854.5153	$854.51	$854.50	$854.60