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	$151.78	13.570%	$172.3765	$172.38	$172.40	$172.40
Purchase #2	$114.72	11.813%	$128.2719	$128.27	$128.25	$128.30
Purchase #3	$186.93	11.772%	$208.9354	$208.94	$208.95	$208.90
Purchase #4	$244.44	9.599%	$267.9038	$267.90	$267.90	$267.90
Purchase #5	$12.69	13.148%	$14.3585	$14.36	$14.35	$14.40
Purchase #6	$78.34	11.828%	$87.6061	$87.61	$87.60	$87.60
Purchase #7	$203.87	10.604%	$225.4884	$225.49	$225.50	$225.50
7 purchase totals =	$992.77		$1,104.9406	$1,104.95	$1,104.95	$1,105.00