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	$142.57	6.278%	$151.5205	$151.52	$151.50	$151.50
Purchase #2	$207.32	8.764%	$225.4895	$225.49	$225.50	$225.50
Purchase #3	$18.85	5.443%	$19.876	$19.88	$19.90	$19.90
Purchase #4	$201.83	3.519%	$208.9324	$208.93	$208.95	$208.90
Purchase #5	$141.25	12.376%	$158.7311	$158.73	$158.75	$158.70
Purchase #6	$117.39	5.250%	$123.553	$123.55	$123.55	$123.60
Purchase #7	$109.93	12.240%	$123.3854	$123.39	$123.40	$123.40
7 purchase totals =	$939.14		$1,011.4879	$1,011.49	$1,011.55	$1,011.50