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	$104.37	11.152%	$116.0093	$116.01	$116.00	$116.00
Purchase #2	$57.42	7.675%	$61.827	$61.83	$61.85	$61.80
Purchase #3	$207.94	9.496%	$227.686	$227.69	$227.70	$227.70
Purchase #4	$161.43	3.227%	$166.6393	$166.64	$166.65	$166.60
Purchase #5	$22.59	13.270%	$25.5877	$25.59	$25.60	$25.60
Purchase #6	$248.97	8.612%	$270.4113	$270.41	$270.40	$270.40
Purchase #7	$80.71	10.800%	$89.4267	$89.43	$89.45	$89.40
7 purchase totals =	$883.43		$957.5873	$957.60	$957.65	$957.50