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	$146.26	6.721%	$156.0901	$156.09	$156.10	$156.10
Purchase #2	$238.57	13.253%	$270.1877	$270.19	$270.20	$270.20
Purchase #3	$74.60	5.727%	$78.8723	$78.87	$78.85	$78.90
Purchase #4	$118.37	11.394%	$131.8571	$131.86	$131.85	$131.90
Purchase #5	$214.37	9.602%	$234.9538	$234.95	$234.95	$235.00
Purchase #6	$107.58	11.579%	$120.0367	$120.04	$120.05	$120.00
Purchase #7	$132.83	7.292%	$142.516	$142.52	$142.50	$142.50
7 purchase totals =	$1,032.58		$1,134.5137	$1,134.52	$1,134.50	$1,134.60