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	$140.91	4.343%	$147.0297	$147.03	$147.05	$147.00
Purchase #2	$216.78	6.758%	$231.43	$231.43	$231.45	$231.40
Purchase #3	$182.38	3.264%	$188.3329	$188.33	$188.35	$188.30
Purchase #4	$158.34	6.486%	$168.6099	$168.61	$168.60	$168.60
Purchase #5	$38.81	3.249%	$40.0709	$40.07	$40.05	$40.10
Purchase #6	$124.61	4.390%	$130.0804	$130.08	$130.10	$130.10
Purchase #7	$151.42	12.530%	$170.3929	$170.39	$170.40	$170.40
7 purchase totals =	$1,013.25		$1,075.9467	$1,075.94	$1,076.00	$1,075.90