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	$167.52	5.542%	$176.804	$176.80	$176.80	$176.80
Purchase #2	$220.27	10.270%	$242.8917	$242.89	$242.90	$242.90
Purchase #3	$127.71	11.853%	$142.8475	$142.85	$142.85	$142.80
Purchase #4	$170.73	12.346%	$191.8083	$191.81	$191.80	$191.80
Purchase #5	$186.35	7.377%	$200.097	$200.10	$200.10	$200.10
Purchase #6	$183.40	8.246%	$198.5232	$198.52	$198.50	$198.50
Purchase #7	$151.51	12.141%	$169.9048	$169.90	$169.90	$169.90
7 purchase totals =	$1,207.49		$1,322.8765	$1,322.87	$1,322.85	$1,322.80