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	$162.32	3.352%	$167.761	$167.76	$167.75	$167.80
Purchase #2	$38.57	9.535%	$42.2476	$42.25	$42.25	$42.20
Purchase #3	$145.43	7.341%	$156.106	$156.11	$156.10	$156.10
Purchase #4	$24.37	6.158%	$25.8707	$25.87	$25.85	$25.90
Purchase #5	$119.32	11.239%	$132.7304	$132.73	$132.75	$132.70
Purchase #6	$214.59	9.379%	$234.7164	$234.72	$234.70	$234.70
Purchase #7	$180.89	8.723%	$196.669	$196.67	$196.65	$196.70
7 purchase totals =	$885.49		$956.1011	$956.11	$956.05	$956.10