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	$246.60	6.370%	$262.3084	$262.31	$262.30	$262.30
Purchase #2	$107.38	10.187%	$118.3188	$118.32	$118.30	$118.30
Purchase #3	$134.47	4.470%	$140.4808	$140.48	$140.50	$140.50
Purchase #4	$175.60	11.232%	$195.3234	$195.32	$195.30	$195.30
Purchase #5	$132.35	6.567%	$141.0414	$141.04	$141.05	$141.00
Purchase #6	$174.52	9.579%	$191.2373	$191.24	$191.25	$191.20
Purchase #7	$146.32	10.822%	$162.1548	$162.15	$162.15	$162.20
7 purchase totals =	$1,117.24		$1,210.8649	$1,210.86	$1,210.85	$1,210.80