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	$129.30	12.824%	$145.8814	$145.88	$145.90	$145.90
Purchase #2	$177.33	13.704%	$201.6313	$201.63	$201.65	$201.60
Purchase #3	$70.84	11.237%	$78.8003	$78.80	$78.80	$78.80
Purchase #4	$147.61	7.437%	$158.5878	$158.59	$158.60	$158.60
Purchase #5	$113.34	12.724%	$127.7614	$127.76	$127.75	$127.80
Purchase #6	$213.60	3.691%	$221.484	$221.48	$221.50	$221.50
Purchase #7	$90.35	10.137%	$99.5088	$99.51	$99.50	$99.50
7 purchase totals =	$942.37		$1,033.6550	$1,033.65	$1,033.70	$1,033.70