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	$96.92	6.810%	$103.5203	$103.52	$103.50	$103.50
Purchase #2	$41.90	7.536%	$45.0576	$45.06	$45.05	$45.10
Purchase #3	$240.29	8.785%	$261.3995	$261.40	$261.40	$261.40
Purchase #4	$228.88	11.691%	$255.6384	$255.64	$255.65	$255.60
Purchase #5	$104.28	12.149%	$116.949	$116.95	$116.95	$116.90
Purchase #6	$88.37	11.570%	$98.5944	$98.59	$98.60	$98.60
Purchase #7	$93.39	9.736%	$102.4825	$102.48	$102.50	$102.50
7 purchase totals =	$894.03		$983.6417	$983.64	$983.65	$983.60