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	$131.93	9.345%	$144.2589	$144.26	$144.25	$144.30
Purchase #2	$169.56	8.369%	$183.7505	$183.75	$183.75	$183.80
Purchase #3	$240.42	6.246%	$255.4366	$255.44	$255.45	$255.40
Purchase #4	$68.96	13.479%	$78.2551	$78.26	$78.25	$78.30
Purchase #5	$200.78	11.323%	$223.5143	$223.51	$223.50	$223.50
Purchase #6	$231.89	7.392%	$249.0313	$249.03	$249.05	$249.00
Purchase #7	$47.65	12.517%	$53.6144	$53.61	$53.60	$53.60
7 purchase totals =	$1,091.19		$1,187.8611	$1,187.86	$1,187.85	$1,187.90