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	$132.27	7.643%	$142.3794	$142.38	$142.40	$142.40
Purchase #2	$141.31	5.733%	$149.4113	$149.41	$149.40	$149.40
Purchase #3	$144.73	11.380%	$161.2003	$161.20	$161.20	$161.20
Purchase #4	$83.90	6.617%	$89.4517	$89.45	$89.45	$89.50
Purchase #5	$27.73	3.523%	$28.7069	$28.71	$28.70	$28.70
Purchase #6	$20.85	11.686%	$23.2865	$23.29	$23.30	$23.30
Purchase #7	$147.78	13.354%	$167.5145	$167.51	$167.50	$167.50
7 purchase totals =	$698.57		$761.9506	$761.95	$761.95	$762.00