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	$234.92	12.193%	$263.5638	$263.56	$263.55	$263.60
Purchase #2	$33.56	13.136%	$37.9684	$37.97	$37.95	$38.00
Purchase #3	$189.82	9.726%	$208.2819	$208.28	$208.30	$208.30
Purchase #4	$88.45	12.409%	$99.4258	$99.43	$99.45	$99.40
Purchase #5	$107.82	5.326%	$113.5625	$113.56	$113.55	$113.60
Purchase #6	$188.63	11.642%	$210.5903	$210.59	$210.60	$210.60
Purchase #7	$75.68	8.126%	$81.8298	$81.83	$81.85	$81.80
7 purchase totals =	$918.88		$1,015.2225	$1,015.22	$1,015.25	$1,015.30