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	$52.81	3.368%	$54.5886	$54.59	$54.60	$54.60
Purchase #2	$241.91	5.387%	$254.9417	$254.94	$254.95	$254.90
Purchase #3	$159.57	8.825%	$173.6521	$173.65	$173.65	$173.70
Purchase #4	$248.90	4.183%	$259.3115	$259.31	$259.30	$259.30
Purchase #5	$158.56	6.506%	$168.8759	$168.88	$168.90	$168.90
Purchase #6	$132.51	4.806%	$138.8784	$138.88	$138.90	$138.90
Purchase #7	$25.43	9.687%	$27.8934	$27.89	$27.90	$27.90
7 purchase totals =	$1,019.69		$1,078.1416	$1,078.14	$1,078.20	$1,078.20