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	$51.71	11.823%	$57.8237	$57.82	$57.80	$57.80
Purchase #2	$159.39	4.492%	$166.5498	$166.55	$166.55	$166.50
Purchase #3	$140.61	6.486%	$149.73	$149.73	$149.75	$149.70
Purchase #4	$189.25	10.386%	$208.9055	$208.91	$208.90	$208.90
Purchase #5	$240.71	3.226%	$248.4753	$248.48	$248.50	$248.50
Purchase #6	$163.76	5.308%	$172.4524	$172.45	$172.45	$172.50
Purchase #7	$198.35	10.605%	$219.385	$219.39	$219.40	$219.40
7 purchase totals =	$1,143.78		$1,223.3217	$1,223.33	$1,223.35	$1,223.30