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	$66.30	10.732%	$73.4153	$73.42	$73.40	$73.40
Purchase #2	$83.95	7.656%	$90.3772	$90.38	$90.40	$90.40
Purchase #3	$154.77	7.759%	$166.7786	$166.78	$166.80	$166.80
Purchase #4	$186.94	11.388%	$208.2287	$208.23	$208.25	$208.20
Purchase #5	$65.73	3.788%	$68.2199	$68.22	$68.20	$68.20
Purchase #6	$186.48	5.311%	$196.384	$196.38	$196.40	$196.40
Purchase #7	$168.61	7.704%	$181.5997	$181.60	$181.60	$181.60
7 purchase totals =	$912.78		$985.0034	$985.01	$985.05	$985.00