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	$113.53	9.280%	$124.0656	$124.07	$124.05	$124.10
Purchase #2	$145.57	13.615%	$165.3894	$165.39	$165.40	$165.40
Purchase #3	$155.54	10.632%	$172.077	$172.08	$172.10	$172.10
Purchase #4	$46.81	11.322%	$52.1098	$52.11	$52.10	$52.10
Purchase #5	$131.43	8.419%	$142.4951	$142.50	$142.50	$142.50
Purchase #6	$110.98	13.215%	$125.646	$125.65	$125.65	$125.60
Purchase #7	$98.43	5.239%	$103.5867	$103.59	$103.60	$103.60
7 purchase totals =	$802.29		$885.3696	$885.39	$885.40	$885.40