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	$165.39	4.403%	$172.6721	$172.67	$172.65	$172.70
Purchase #2	$148.95	4.398%	$155.5008	$155.50	$155.50	$155.50
Purchase #3	$169.90	5.411%	$179.0933	$179.09	$179.10	$179.10
Purchase #4	$57.80	5.409%	$60.9264	$60.93	$60.95	$60.90
Purchase #5	$72.92	7.297%	$78.241	$78.24	$78.25	$78.20
Purchase #6	$42.38	3.489%	$43.8586	$43.86	$43.85	$43.90
Purchase #7	$18.85	9.116%	$20.5684	$20.57	$20.55	$20.60
7 purchase totals =	$676.19		$710.8606	$710.86	$710.85	$710.90