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	$151.36	3.667%	$156.9104	$156.91	$156.90	$156.90
Purchase #2	$239.95	9.348%	$262.3805	$262.38	$262.40	$262.40
Purchase #3	$11.75	3.497%	$12.1609	$12.16	$12.15	$12.20
Purchase #4	$248.57	3.602%	$257.5235	$257.52	$257.50	$257.50
Purchase #5	$248.59	4.294%	$259.2645	$259.26	$259.25	$259.30
Purchase #6	$185.43	4.551%	$193.8689	$193.87	$193.85	$193.90
Purchase #7	$33.96	9.848%	$37.3044	$37.30	$37.30	$37.30
7 purchase totals =	$1,119.61		$1,179.4131	$1,179.40	$1,179.35	$1,179.50