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	$227.90	3.793%	$236.5442	$236.54	$236.55	$236.50
Purchase #2	$52.89	5.126%	$55.6011	$55.60	$55.60	$55.60
Purchase #3	$20.33	4.464%	$21.2375	$21.24	$21.25	$21.20
Purchase #4	$113.31	5.265%	$119.2758	$119.28	$119.30	$119.30
Purchase #5	$145.45	8.849%	$158.3209	$158.32	$158.30	$158.30
Purchase #6	$249.35	8.155%	$269.6845	$269.68	$269.70	$269.70
Purchase #7	$182.55	5.350%	$192.3164	$192.32	$192.30	$192.30
7 purchase totals =	$991.78		$1,052.9804	$1,052.98	$1,053.00	$1,052.90