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	$126.83	13.548%	$144.0129	$144.01	$144.00	$144.00
Purchase #2	$110.64	11.480%	$123.3415	$123.34	$123.35	$123.30
Purchase #3	$52.98	5.346%	$55.8123	$55.81	$55.80	$55.80
Purchase #4	$21.79	11.337%	$24.2603	$24.26	$24.25	$24.30
Purchase #5	$192.37	5.672%	$203.2812	$203.28	$203.30	$203.30
Purchase #6	$100.31	11.221%	$111.5658	$111.57	$111.55	$111.60
Purchase #7	$88.46	4.677%	$92.5973	$92.60	$92.60	$92.60
7 purchase totals =	$693.38		$754.8713	$754.87	$754.85	$754.90