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	$159.36	5.149%	$167.5654	$167.57	$167.55	$167.60
Purchase #2	$184.33	7.709%	$198.54	$198.54	$198.55	$198.50
Purchase #3	$141.69	12.190%	$158.962	$158.96	$158.95	$159.00
Purchase #4	$25.64	6.395%	$27.2797	$27.28	$27.30	$27.30
Purchase #5	$66.60	10.369%	$73.5058	$73.51	$73.50	$73.50
Purchase #6	$144.78	9.501%	$158.5355	$158.54	$158.55	$158.50
Purchase #7	$99.37	5.614%	$104.9486	$104.95	$104.95	$104.90
7 purchase totals =	$821.77		$889.3370	$889.35	$889.35	$889.30