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	$108.96	13.579%	$123.7557	$123.76	$123.75	$123.80
Purchase #2	$185.46	11.327%	$206.4671	$206.47	$206.45	$206.50
Purchase #3	$54.38	6.675%	$58.0099	$58.01	$58.00	$58.00
Purchase #4	$174.79	12.239%	$196.1825	$196.18	$196.20	$196.20
Purchase #5	$123.99	12.268%	$139.2011	$139.20	$139.20	$139.20
Purchase #6	$195.95	13.124%	$221.6665	$221.67	$221.65	$221.70
Purchase #7	$190.35	10.264%	$209.8875	$209.89	$209.90	$209.90
7 purchase totals =	$1,033.88		$1,155.1703	$1,155.18	$1,155.15	$1,155.30