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	$59.75	10.209%	$65.8499	$65.85	$65.85	$65.80
Purchase #2	$208.90	9.859%	$229.4955	$229.50	$229.50	$229.50
Purchase #3	$211.67	6.716%	$225.8858	$225.89	$225.90	$225.90
Purchase #4	$162.40	4.275%	$169.3426	$169.34	$169.35	$169.30
Purchase #5	$237.46	12.511%	$267.1686	$267.17	$267.15	$267.20
Purchase #6	$57.58	13.648%	$65.4385	$65.44	$65.45	$65.40
Purchase #7	$242.39	6.113%	$257.2073	$257.21	$257.20	$257.20
7 purchase totals =	$1,180.15		$1,280.3882	$1,280.40	$1,280.40	$1,280.30