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	$104.86	10.634%	$116.0108	$116.01	$116.00	$116.00
Purchase #2	$213.52	3.332%	$220.6345	$220.63	$220.65	$220.60
Purchase #3	$250.79	5.103%	$263.5878	$263.59	$263.60	$263.60
Purchase #4	$144.97	13.485%	$164.5192	$164.52	$164.50	$164.50
Purchase #5	$235.27	11.302%	$261.8602	$261.86	$261.85	$261.90
Purchase #6	$130.26	9.240%	$142.296	$142.30	$142.30	$142.30
Purchase #7	$107.34	11.740%	$119.9417	$119.94	$119.95	$119.90
7 purchase totals =	$1,187.01		$1,288.8502	$1,288.85	$1,288.85	$1,288.80