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	$222.89	7.585%	$239.7962	$239.80	$239.80	$239.80
Purchase #2	$19.94	9.133%	$21.7611	$21.76	$21.75	$21.80
Purchase #3	$100.43	11.867%	$112.348	$112.35	$112.35	$112.30
Purchase #4	$181.96	13.732%	$206.9467	$206.95	$206.95	$206.90
Purchase #5	$79.32	13.812%	$90.2757	$90.28	$90.30	$90.30
Purchase #6	$80.90	10.546%	$89.4317	$89.43	$89.45	$89.40
Purchase #7	$41.53	7.360%	$44.5866	$44.59	$44.60	$44.60
7 purchase totals =	$726.97		$805.1460	$805.16	$805.20	$805.10