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	$147.84	13.262%	$167.4465	$167.45	$167.45	$167.40
Purchase #2	$14.37	8.556%	$15.5995	$15.60	$15.60	$15.60
Purchase #3	$74.50	5.370%	$78.5007	$78.50	$78.50	$78.50
Purchase #4	$246.93	6.861%	$263.8719	$263.87	$263.85	$263.90
Purchase #5	$58.88	13.583%	$66.8777	$66.88	$66.90	$66.90
Purchase #6	$132.72	11.452%	$147.9191	$147.92	$147.90	$147.90
Purchase #7	$163.71	10.867%	$181.5004	$181.50	$181.50	$181.50
7 purchase totals =	$838.95		$921.7158	$921.72	$921.70	$921.70